💎SQL Reloaded: Query Writing I (Best Practices)

In general, when creating queries, the following best practices should be considered:
- Use ANSI-compliant syntax as much as possible.
- Use aliases for all the tables.
- Design for performance reusability and security.
- Reduce unnecessary network traffic.
- Group together the attributes coming from the same table.
- Rename columns in order to avoid confusion, though don’t overreact with this practice.
- Use uniform coding style, formatting and naming conventions
- Use indexed join predicates.
- Learn about the strengths/weaknesses of each feature before using it.
- Use versioning & keep older versions. - Test the queries.
- Write unit tests first [2].
- Handle missing values (NULLs).
- Document database objects inline and specific documents (e.g. Data Dictionaries, Functional Specifications).
- Refactor code
- Use SQL tunings tools.
- Write tiny chunks of code: encapsulate formulas and business logic in functions [2], avoid inline scalar functions.
- Defensive coding: use exception handling, consider all scenarios.


Things to avoid:
- Complex expressions in search conditions [1].
- Join predicates on expressions [1].
- Expressions over columns in local predicated [1].
- Data types mismatches on join columns [1].
- Non-equality join predicates [1].
- Unnecessary outer joins [1].
- Redundant predicates [1].
- Multiple aggregations with DISTINCT.
- Build queries dynamically unless necessary.
- Techniques that use full-table scan: functions that don’t use/perform poor on indexes, wildcards at the beginning of a word.
- Use more attributes/records than needed (particular case: Use * instead of specifying the attributes).
- Using nested views.
- Rely entirely on the code created by wizards and other automation tools.
- UNION unless really needed: use UNION ALL.
- UNIONS instead of conditional-base code (e.g. CASE, DECODE) or self-joins.
- Using temporary tables.
- Server side cursors.
- Procedural queries (e.g. loops, cursors) rather than using set-based queries.
- Redundant logic/code.
- Negations on constraints.
- Code facilitating SQL injection: use parameterized objects.
- Hard-coding values.
- Undocumented functionality.
- Use GROUP BY on final sub-query when it could be used in a sub-query.
- Multiple self-joins/joins to same table instead of GROUP BY.
- Repetitive calls to the same function and same parameters.
- Use constants in ORDER BY clause.
- Create too many versions of the same query.


Note:
Please note that there are situations and situations, a technique not recommended in general could prove to offer better performance than alternatives (e.g. : recursive simulation + temporary table vs. hierarchical self-joins on SQL Server 2000 ), while for others there are several aspects that need to be considered, for example the trade in performance vs. reusability. Even if most of the database vendors adhere to SQL ANSI standard, in the end each functionality could be implemented differently and vendors could provide additional functionality, therefore could be considered specific best practices for each functionality/vendor.

References:
[1] IBM (2010) Best Practice - Writing and Tuning Queries for Optimal Performance [link]
[2] Oracle (2009) Cleaning Up PL/SQL Practices, by S. Feuerstein [link]

Resources:
Microsoft TechNet. (2010). SQL Server - Best Practices [link]

🏗️Software Engineering: Features (Just the Quotes)

"Extra features were once considered desirable. We now recognize that 'free' features are rarely free. Any increase in generality that does not contribute to reliability, modularity, maintainability, and robustness should be suspected." (Boris Beizer, "Software Testing Techniques", 1990)

"Design bugs are often subtle and occur by evolution with early assumptions being forgotten as new features or uses are added to systems." (Fernando J Corbató, "On Building Systems That Will Fail", 1991)

"When you find you have to add a feature to a program, and the program's code is not structured in a convenient way to add the feature, first refactor the program to make it easy to add the feature, then add the feature." (Martin Fowler, "Refactoring: Improving the Design of Existing Code", 1999)

"One of the purposes of planning is we always want to work on the most valuable thing possible at any given time. We can’t pick features at random and expect them to be most valuable. We have to begin development by taking a quick look at everything that might be valuable, putting all our cards on the table. At the beginning of each iteration the business (remember the balance of power) will pick the most valuable features for the next iteration." (Kent Beck & Martin Fowler, "Planning Extreme Programming", 2000)

"Putting a new feature into a program is important, but refactoring so new features can be added in the future is equally important." (Ward Cunningham, "Crucible of Creativity", 2005)

"Developing fewer features allows you to conserve development resources and spend more time refining those features that users really need. Fewer features mean fewer things to confuse users, less risk of user errors, less description and documentation, and therefore simpler Help content. Removing any one feature automatically increases the usability of the remaining ones." (Jakob Nielsen, "Prioritizing Web Usability", 2006) 

"Features have a specification cost, a design cost, and a development cost. There is a testing cost and a reliability cost. […] Features have a documentation cost. Every feature adds pages to the manual increasing training costs." (Douglas Crockford, "JavaScript: The Good Parts: The Good Parts", 2008)

"Features that offer value to a minority of users impose a cost on all users." (Douglas Crockford, "JavaScript: The Good Parts", 2008)

"In an ideal system, we incorporate new features by extending the system, not by making modifications to existing code." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"We see a lot of feature-driven product design in which the cost of features is not properly accounted. Features can have a negative value to customers because they make the products more difficult to understand and use. We are finding that people like products that just work. It turns out that designs that just work are much harder to produce that designs that assemble long lists of features." (Douglas Crockford, "JavaScript: The Good Parts", 2008)

"Technical debt is like a loan: you benefit from it in the short term, but you have to pay interest on it until it is fully paid off. Shortcuts in the code make it harder to add features or refactor your code. They are breeding grounds for defects and brittle test cases. The longer you leave it, the worse it gets." (Seb Rose [in Kevlin Henney’s "97 Things Every Programmer Should Know", 2010]) 

🏗️Software Engineering: Refactoring (Just the Quotes)

"When you feel the need to write a comment, first try to refactor the code so that any comment becomes superfluous." (Kent Beck, "Refactoring: Improving the Design of Existing Code", 1999)

"When you find you have to add a feature to a program, and the program's code is not structured in a convenient way to add the feature, first refactor the program to make it easy to add the feature, then add the feature."  (Kent Beck, "Refactoring: Improving the Design of Existing Code", 1999)

"Unit tests can be tedious to write, but they save you time in the future (by catching bugs after changes). Less obviously, but just as important, is that they can save you time now: tests focus your design and implementation on simplicity, they support refactoring, and they validate features as you develop." (Ron Jeffries, "Extreme Programming Installed, 2001)

"Before you start refactoring, check that you have a solid suite of tests. These tests must be self-checking." (Martin Fowler et al, "Refactoring: Improving the Design of Existing Code", 2002)

"Given software engineers’ infatuation with indirection, it may not surprise you to learn that most refactoring introduces more indirection into a program. Refactoring tends to break big objects into several smaller ones and big methods into several smaller ones." (Kent Beck, "Indirection and Refactoring", 2002)

"One problem area for refactoring is databases. Most business applications are tightly coupled to the database schema that supports them. That's one reason that the database is difficult to change. Another reason is data migration. Even if you have carefully layered your system to minimize the dependencies between the database schema and the object model, changing the database schema forces you to migrate the data, which can be a long and fraught task." (Martin Fowler et al, "Refactoring: Improving the Design of Existing Code", 2002)

"Refactoring is risky. It requires changes to working code that can introduce subtle bugs. Refactoring, if not done properly, can set you back days, even weeks. And refactoring becomes riskier when practiced informally or ad hoc." (Erich Gamma, 2002)

"Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure. It is a disciplined way to clean up code that minimizes the chances of introducing bugs. In essence when you refactor you are improving the design of the code after it has been written." (Martin Fowler et al, "Refactoring: Improving the Design of Existing Code", 2002)

"Refactoring is the process of taking a running program and adding to its value, not by changing its behavior but by giving it more of these qualities that enable us to continue developing at speed." (Kent Beck, "Why Refactoring Works", 2002)

"Refactoring changes the programs in small steps. If you make a mistake, it is easy to find the bug." (Martin Fowler et al, "Refactoring: Improving the Design of Existing Code", 2002)

"Without refactoring, the design of the program will decay. As people change code - changes to realize short-term goals or changes made without a full comprehension of the design of the code - the code loses its structure. It becomes harder to see the design by reading the code. Refactoring is rather like tidying up the code. Work is done to remove bits that aren't really in the right place. Loss of the structure of code has a cumulative effect. The harder it is to see the design in the code, the harder it is to preserve it, and the more rapidly it decays. Regular refactoring helps code retain its shape." (Martin Fowler et al, "Refactoring: Improving the Design of Existing Code", 2002)

"A commitment to simplicity of design means addressing the essence of design - the abstractions on which software is built - explicitly and up front. Abstractions are articulated, explained, reviewed and examined deeply, in isolation from the details of the implementation. This doesn’t imply a waterfall process, in which all design and specification precedes all coding. But developers who have experienced the benefits of this separation of concerns are reluctant to rush to code, because they know that an hour spent on designing abstractions can save days of refactoring." (Daniel Jackson, "Software Abstractions", 2006)

"To programmers, refactoring means rewriting a chunk of code to make it briefer, clearer, and easier to read without changing what it actually does. Refactoring is often compared to gardening; it is never finished." (Scott Rosenberg, "Dreaming in Code", 2007)

"It is a myth that we can get systems 'right the first time'. Instead, we should implement only today’s stories, then refactor and expand the system to implement new stories tomorrow. This is the essence of iterative and incremental agility. Test-driven development, refactoring, and the clean code they produce make this work at the code level." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Refactoring is a lot like solving a Rubik’s cube. There are lots of little steps required to achieve a large goal. Each step enables the next." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Refactoring is the process of improving the design of existing code without changing its behavior. [...] Bug fixing often uncovers opportunities for refactoring. The very fact that you’re working with code that contains a bug indicates that there is a chance that it could be clearer or better structured." (Paul Butcher, "Debug It! Find, Repair, and Prevent Bugs in Your Code", 2009)

"Although it is focused on the code, refactoring has a large impact on the design of a system. It is vital for senior designers and architects to understand the principles of refactoring and to use them in their projects." (Jay Fields et al, "Refactoring: Ruby Edition", 2010)

"Don’t be afraid of your code. Who cares if something gets temporarily broken while you move things around? A paralyzing fear of change is what got your project into this state to begin with. Investing the time to refactor will pay for itself several times over the lifecycle of your project. An added benefit is that your team’s experience dealing with the sick system makes you all experts in knowing how it should work. Apply this knowledge rather than resent it. Working on a system you hate is not how anybody should have to spend his time." (Mike Lewis, [in Kevlin Henney’s "97 Things Every Programmer Should Know", 2010])

"New technology is an insufficient reason to refactor. One of the worst reasons to refactor is because the current code is way behind all the cool technology we have today, and we believe that a new language or framework can do things a lot more elegantly. Unless a cost-benefit analysis shows that a new language or framework will result in significant improvements in functionality, maintainability, or productivity, it is best to leave it as it is." (Rajith Attapattu [in Kevlin Henney’s "97 Things Every Programmer Should Know", 2010])

"Refactoring is the process of changing a software system in such a way that it does not alter the external behavior of the code yet improves its internal structure. It is a disciplined way to clean up code that minimizes the chances of introducing bugs. In essence when you refactor you are improving the design of the code after it has been written." (Jay Fields et al, "Refactoring: Ruby Edition", 2010)

"Technical debt is like a loan: you benefit from it in the short term, but you have to pay interest on it until it is fully paid off. Shortcuts in the code make it harder to add features or refactor your code. They are breeding grounds for defects and brittle test cases. The longer you leave it, the worse it gets." (Seb Rose [in Kevlin Henney’s "97 Things Every Programmer Should Know", 2010]) 

"What can you do to actually make your code tell the truth as clearly as possible? Strive for good names. Structure your code with respect to cohesive functionality, which also eases naming. Decouple your code to achieve orthogonality. Write automated tests explaining the intended behavior and check the interfaces. Refactor mercilessly when you learn how to code a simpler, better solution. Make your code as simple as possible to read and understand." (Peter Sommerlad, [in Kevlin Henney’s "97 Things Every Programmer Should Know", 2010])

"When an engineer refactors the internals of a system without modifying its interface, whether for performance, clarity, or any other reason, the system’s tests shouldn’t need to change. The role of tests in this case is to ensure that the refactoring didn’t change the system’s behavior. Tests that need to be changed during a refactoring indicate that either the change is affecting the system’s behavior and isn’t a pure refactoring, or that the tests were not written at an appropriate level of abstraction." (Titus Winters, "Software Engineering at Google: Lessons Learned from Programming Over Time", 2020)

🌁Software Engineering: Maintainability (Definitions)

"The ease of maintenance that a program’s author puts into the program by writing clear code." (Greg Perry, "Sams Teach Yourself Beginning Programming in 24 Hours" 2nd Ed., 2001)

"The characteristic of an information environment to be manageable at reasonable costs in terms of content volume, frequency, quality, and infrastructure. If a system is maintainable, information can be added, deleted, or changed efficiently." (Martin J Eppler, "Managing Information Quality" 2nd Ed., 2006)

"a measure of how quickly and effectively a CI/service can be restored to normal after a failure." (ITIL)

 Maintainability is defined as the probability that a system or system element can be repaired in a defined environment with defined resources within a specified period of time. Increased maintainability implies shorter repair times. (Created for SEBoK)

"The capability of the software product to adhere to standards or conventions relating to maintainability." (Software Quality Assurance)

"The ease with which a software product can be modified to correct defects, modified to meet new requirements, modified to make future maintenance easier, or adapted to a changed environment." (ISO 9126)

"The probability that a given maintenance action for an item under given usage conditions can be performed within a stated time interval when the maintenance is performed under stated conditions using stated procedures and resources." (ASQ)

"The process of testing to determine the maintainability of a software product." (ISTQB)

⛩️Robert C Martin - Collected Quotes

"A system that is comprehensively tested and passes all of its tests all of the time is a testable system. That’s an obvious statement, but an important one. Systems that aren’t testable aren’t verifiable. Arguably, a system that cannot be verified should never be deployed." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Any comment that forces you to look in another module for the meaning of that comment has failed to communicate to you and is not worth the bits it consumes." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008) 

"Clean code is focused. Each function, each class, each module exposes a single-minded attitude that remains entirely undistracted, and unpolluted, by the surrounding details."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Clean code is not written by following a set of rules. You don’t become a software craftsman by learning a list of heuristics. Professionalism and craftsmanship come from values that drive disciplines." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Code formatting is important. It is too important to ignore and it is too important to treat religiously. Code formatting is about communication, and communication is the professional developer’s first order of business."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Duplication is the primary enemy of a well-designed system. It represents additional work, additional risk, and additional unnecessary complexity."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Every system is built from a domain-specific language designed by the programmers to describe that system. Functions are the verbs of that language, and classes are the nouns."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Good software designs accommodate change without huge investments and rework. When we use code that is out of our control, special care must be taken to protect our investment and make sure future change is not too costly."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"If the discipline of requirements specification has taught us anything, it is that well-specified requirements are as formal as code and can act as executable tests of that code!"  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"In an ideal system, we incorporate new features by extending the system, not by making modifications to existing code." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Indeed, the ratio of time spent reading versus writing is well over 10 to 1. We are constantly reading old code as part of the effort to write new code. [… Therefore,] making it easy to read makes it easier to write." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008) 

"It is a myth that we can get systems 'right the first time'. Instead, we should implement only today’s stories, then refactor and expand the system to implement new stories tomorrow. This is the essence of iterative and incremental agility. Test-driven development, refactoring, and the clean code they produce make this work at the code level." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"It is not enough for code to work. Code that works is often badly broken. Programmers who satisfy themselves with merely working code are behaving unprofessionally. They may fear that they don’t have time to improve the structure and design of their code, but I disagree. Nothing has a more profound and long-term degrading effect upon a development project than bad code." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"It is unit tests that keep our code flexible, maintainable, and reusable. The reason is simple. If you have tests, you do not fear making changes to the code! Without tests every change is a possible bug."  (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Nothing has a more profound and long-term degrading effect upon a development project than bad code. Bad schedules can be redone, bad requirements can be redefined. Bad team dynamics can be repaired. But bad code rots and ferments, becoming an inexorable weight that drags the team down." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"One difference between a smart programmer and a professional programmer is that the professional understands that clarity is king. Professionals use their powers for good and write code that others can understand." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008) 

"One of the best ways to ruin a program is to make massive changes to its structure in the name of improvement. Some programs never recover from such “improvements.” The problem is that it’s very hard to get the program working the same way it worked before the 'improvement'." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Refactoring is a lot like solving a Rubik’s cube. There are lots of little steps required to achieve a large goal. Each step enables the next." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Standards make it easier to reuse ideas and components, recruit people with relevant experience, encapsulate good ideas, and wire components together. However, the process of creating standards can sometimes take too long for industry to wait, and some standards lose touch with the real needs of the adopters they are intended to serve." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"The majority of the cost of a software project is in long-term maintenance. In order to minimize the potential for defects as we introduce change, it’s critical for us to be able to understand what a system does. As systems become more complex, they take more and more time for a developer to understand, and there is an ever greater opportunity for a misunderstanding. Therefore, code should clearly express the intent of its author. The clearer the author can make the code, the less time others will have to spend understanding it. This will reduce defects and shrink the cost of maintenance." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"The problem isn’t the simplicity of the code but the implicity of the code (to coin a phrase): the degree to which the context is not explicit in the code itself." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"There are two parts to learning craftsmanship: knowledge and work. You must gain the knowledge of principles, patterns, practices, and heuristics that a craftsman knows, and you must also grind that knowledge into your fingers, eyes, and gut by working hard and practicing." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"We do not want to expose the details of our data. Rather we want to express our data in abstract terms. This is not merely accomplished by using interfaces and/or getters and setters. Serious thought needs to be put into the best way to represent the data that an object contains. The worst option is to blithely add getters and setters." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"When people look under the hood, we want them to be impressed with the neatness, consistency, and attention to detail that they perceive. We want them to be struck by the orderliness. We want their eyebrows to rise as they scroll through the modules. We want them to perceive that professionals have been at work. If instead they see a scrambled mass of code that looks like it was written by a bevy of drunken sailors, then they are likely to conclude that the same inattention to detail pervades every other aspect of the project." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Whether you are designing systems or individual modules, never forget to use the simplest thing that can possibly work." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Yet attentiveness to detail is an even more critical foundation of professionalism than is any grand vision. First, it is through practice in the small that professionals gain proficiency and trust for practice in the large. Second, the smallest bit of sloppy construction, of the door that does not close tightly or the slightly crooked tile on the floor, or even the messy desk, completely dispels the charm of the larger whole. That is what clean code is about." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"You should choose a set of simple rules that govern the format of your code, and then you should consistently apply those rules. If you are working on a team, then the team should agree to a single set of formatting rules and all members should comply." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Acceptance tests are not unit tests. Unit tests are written by programmers for programmers. They are formal design documents that describe the lowest level structure and behavior of the code. The audience is programmers, not business. Acceptance tests are written by the business for the business (even when you, the developer, end up writing them). They are formal requirements documents that specify how the system should behave from the business’ point of view. The audience is the business and the programmers." (Robert C Martin, "Clean Code: A Handbook of Agile Software Craftsmanship", 2008)

"Coding is an intellectually challenging and exhausting activity. It requires a level of concentration and focus that few other disciplines require. The reason for this is that coding requires you to juggle many competing factors at once." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"Following the principle of 'late precision', acceptance tests should be written as late as possible, typically a few days before the feature is implemented. In Agile projects, the tests are written after the features have been selected for the next Iteration or Sprint." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"For some reason software developers don’t think of debugging time as coding time. They think of debugging time as a call of nature, something that just has to be done. But debugging time is just as expensive to the business as coding time is, and therefore anything we can do to avoid or diminish it is good." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"One of the most common communication issues between programmers and business is the requirements. The business people state what they believe they need, and then the programmers build what they believe the business described. At least that’s how it’s supposed to work. In reality, the communication of requirements is extremely difficult, and the process is fraught with error." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"One of the worst symptoms of a dysfunctional team is when each programmer builds a wall around his code and refuses to let other programmers touch it." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"Programming is an act of creation. When we write code we are creating something out of nothing. We are boldly imposing order upon chaos. We are confidently commanding, in precise detail, the behaviors of a machine that could otherwise do incalculable damage. And so, programming is an act of supreme arrogance." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"Software development is a marathon, not a sprint. You can’t win the race by trying to run as fast as you can from the outset. You win by conserving your resources and pacing yourself. A marathon runner takes care of her body both before and during the race. Professional programmers conserve their energy and creativity with the same care." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The cost of automating acceptance tests is so small in comparison to the cost of executing manual test plans that it makes no economic sense to write scripts for humans to execute. Professional developers take responsibility for their part in ensuring that acceptance tests are automated." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The fact that bugs will certainly occur in your code does not mean you aren’t responsible for them. The fact that the task to write perfect software is virtually impossible does not mean you aren’t responsible for the imperfection." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The fundamental assumption underlying all software projects is that software is easy to change. If you violate this assumption by creating inflexible structures, then you undercut the economic model that the entire industry is based on." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The purpose of acceptance tests is communication, clarity, and precision. By agreeing to them, the developers, stakeholders, and testers all understand what the plan for the system behavior is. Achieving this kind of clarity is the responsibility of all parties. Professional developers make it their responsibility to work with stakeholders and testers to ensure that all parties know what is about to be built." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The second best way to learn is to collaborate with other people. Professional software developers make a special effort to program together, practice together, design and plan together. By doing so they learn a lot from each other, and they get more done faster with fewer errors." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"The true professional knows that delivering function at the expense of structure is a fool’s errand. It is the structure of your code that allows it to be flexible. If you compromise the structure, you compromise the future." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"True professionals work hard to keep their skills sharp and ready. It is not enough to simply do your daily job and call that practice. Doing your daily job is performance, not practice. Practice is when you specifically exercise your skills outside of the performance of your job for the sole purpose of refining and enhancing those skills." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"Unfortunately, all too many projects become mired in a tar pit of poor structure. Tasks that used to take days begin to take weeks, and then months. Management, desperate to recapture lost momentum, hires more developers to speed things up. But these developers simply add to the morass, deepening the structural damage and raising the impediment." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011) 

"When you cannot concentrate and focus sufficiently, the code you write will be wrong. It will have bugs. It will have the wrong structure. It will be opaque and convoluted. It will not solve the customers’ real problems. In short, it will have to be reworked or redone. Working while distracted creates waste." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"[…] you should not agree to work overtime unless (1) you can personally afford it, (2) it is short term, two weeks or less, and (3) your boss has a fall-back plan in case the overtime effort fails." (Robert C Martin,"The Clean Coder: A code of conduct for professional programmers", 2011)

"Function or architecture? Which of these two provides the greater value? Is it more important for the software system to work, or is it more important for the software system to be easy to change?" (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"Getting software right is hard. It takes knowledge and skills that most young programmers haven’t yet acquired. It requires thought and insight that most programmers don’t take the time to develop. It requires a level of discipline and dedication that most programmers never dreamed they’d need. Mostly, it takes a passion for the craft and the desire to be a professional." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"Software architects are, by virtue of their job description, more focused on the structure of the system than on its features and functions. Architects create an architecture that allows those features and functions to be easily developed, easily modified, and easily extended." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"The bigger lie that developers buy into is the notion that writing messy code makes them go fast in the short term, and just slows them down in the long term. Developers who accept this lie exhibit the hare’s overconfidence in their ability to switch modes from making messes to cleaning up messes sometime in the future, but they also make a simple error of fact. The fact is that making messes is always slower than staying clean, no matter which time scale you are using." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"The goal of software architecture is to minimize the human resources required to build and maintain the required system." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"What is OO? There are many opinions and many answers to this question. To the software architect, however, the answer is clear: OO is the ability, through the use of polymorphism, to gain absolute control over every source code dependency in the system. It allows the architect to create a plugin architecture, in which modules that contain high-level policies are independent of modules that contain low-level details. The low-level details are relegated to plugin modules that can be deployed and developed independently from the modules that contain high-level policies." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"When software is done right, it requires a fraction of the human resources to create and maintain. Changes are simple and rapid. Defects are few and far between. Effort is minimized, and functionality and flexibility are maximized." (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

"When we talk about software architecture, software is recursive and fractal in nature, etched and sketched in code. Everything is details. Interlocking levels of detail also contribute to a building’s architecture, but it doesn’t make sense to talk about physical scale in software. Software has structure - many structures and many kinds of structures-but its variety eclipses the range of physical structure found in buildings. You can even argue quite convincingly that there is more design activity and focus in software than in building architecture - in this sense, it’s not unreasonable to consider software architecture more architectural than building architecture!" (Robert C Martin, "Clean Architecture: A Craftsman's Guide to Software Structure and Design", 2017)

⛩️Steve C McConnell - Collected Quotes

"An algorithm gives you the instructions directly. A heuristic tells you how to discover the instructions for yourself, or at least where to look for them." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"At the software-architecture level, the complexity of a problem is reduced by dividing the system into subsystems. Humans have an easier time comprehending several simple pieces of information than one complicated piece." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Because successful programming depends on minimizing complexity, a skilled programmer will build in as much flexibility as needed to meet the software's requirements but will not add flexibility - and related complexity - beyond what's required." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"By far the most common project risks in software development are poor requirements and poor project planning, thus preparation tends to focus on improving requirements and project plans."(Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Complexity in all forms - complicated algorithms, large data sets, intricate communications protocols, and so on - is prone to errors. If an error does occur, it will be easier to find if it isn't spread through the code but is localized within a class. Changes arising from fixing the error won't affect other code because only one class will have to be fixed - other code won't be touched. If you find a better, simpler, or more reliable algorithm, it will be easier to replace the old algorithm if it has been isolated into a class. During development, it will be easier to try several designs and keep the one that works best." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Design is sloppy because a good solution is often only subtly different from a poor one." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Encapsulation says that, not only are you allowed to take a simpler view of a complex concept, you are not allowed to look at any of the details of the complex concept. What you see is what you get - it's all you get!" (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"From time to time, a complex algorithm will lead to a longer routine, and in those circumstances, the routine should be allowed to grow organically up to 100–200 lines. (A line is a noncomment, nonblank line of source code.) Decades of evidence say that routines of such length are no more error prone than shorter routines. Let issues such as the routine's cohesion, depth of nesting, number of variables, number of decision points, number of comments needed to explain the routine, and other complexity-related considerations dictate the length of the routine rather than imposing a length restriction per se." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"If you're passing a parameter among several routines, that might indicate a need to factor those routines into a class that share the parameter as object data. Streamlining parameter passing isn't a goal, per se, but passing lots of data around suggests that a different class organization might work better." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"In software, consultants sometimes tell you to buy into certain software-development methods to the exclusion of other methods. That’s unfortunate because if you buy into any single methodology 100 percent, you’ll see the whole world in terms of that methodology. In some instances, you’ll miss opportunities to use other methods better suited to your current problem." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"[...] inheritance is a powerful tool for reducing complexity because a programmer can focus on the generic attributes of an object without worrying about the details. If a programmer must be constantly thinking about semantic differences in subclass implementations, then inheritance is increasing complexity rather than reducing it." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Inheritance is the idea that one class is a specialization of another class. The purpose of inheritance is to create simpler code by defining a base class that specifies common elements of two or more derived classes. The common elements can be routine interfaces, implementations, data members, or data types. Inheritance helps avoid the need to repeat code and data in multiple locations by centralizing it within a base class. When you decide to use inheritance, you have to make several decisions: For each member routine, will the routine be visible to derived classes? Will it have a default implementation? Will the default implementation be overridable? For each data member (including variables, named constants, enumerations, and so on), will the data member be visible to derived classes?" (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Modularity's goal is to make each routine or class like a 'black box': You know what goes in, and you know what comes out, but you don't know what happens inside." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"The concept of modularity is related to information hiding, encapsulation, and other design heuristics. But sometimes thinking about how to assemble a system from a set of black boxes provides insights that information hiding and encapsulation don't, so the concept is worth having in your back pocket." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"The underlying message of all these rules is that inheritance tends to work against the primary technical imperative you have as a programmer, which is to manage complexity. For the sake of controlling complexity, you should maintain a heavy bias against inheritance." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"One of the main differences between programs you develop in school and those you develop as a professional is that the design problems solved by school programs are rarely, if ever, wicked." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Programming assignments in school are devised to move you in a beeline from beginning to end. You'd probably want to tar and feather a teacher who gave you a programming assignment, then changed the assignment as soon as you finished the design, and then changed it again just as you were about to turn in the completed program. But that very process is an everyday reality in professional programming." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Testing by itself does not improve software quality. Test results are an indicator of quality, but in and of themselves, they don't improve it. Trying to improve software quality by increasing the amount of testing is like trying to lose weight by weighing yourself more often. What you eat before you step onto the scale determines how much you will weigh, and the software development techniques you use determine how many errors testing will find. If you want to lose weight, don't buy a new scale; change your diet. If you want to improve your software, don't test more; develop better." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction", 1993)

"The more independent the subsystems are, the more you make it safe to focus on one bit of complexity at a time. Carefully defined objects separate concerns so that you can focus on one thing at a time. Packages provide the same benefit at a higher level of aggregation." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"The most challenging part of programming is conceptualizing the problem, and many errors in programming are conceptual errors." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"The source code is often the only accurate description of the software. On many projects, the only documentation available to programmers is the code itself. Requirements specifications and design documents can go out of date, but the source code is always up to date. Consequently, it's imperative that the code be of the highest possible quality." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"The words available in a programming language for expressing your programming thoughts certainly determine how you express your thoughts and might even determine what thoughts you can express." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"Watch for coupling that's too tight. 'Coupling' refers to how tight the connection is between two classes. In general, the looser the connection, the better. Several general guidelines flow from this concept: Minimize accessibility of classes and members. Avoid friend classes, because they're tightly coupled. Make data private rather than protected in a base class to make derived classes less tightly coupled to the base class. Avoid exposing member data in a class's public interface. Be wary of semantic violations of encapsulation. Observe the 'Law of Demeter' [...]. Coupling goes hand in glove with abstraction and encapsulation. Tight coupling occurs when an abstraction is leaky, or when encapsulation is broken." (Steve C McConnell," Code Complete: A Practical Handbook of Software Construction", 1993)

"A typical software project can present more opportunities to learn from mistakes than some people get in a lifetime." (Steve McConnell, "Rapid Development", 1996)

"Even when you have skilled, motivated, hard-working people, the wrong team structure can undercut their efforts instead of catapulting them to success. A poor team structure can increase development time, reduce quality, damage morale, increase turnover, and ultimately lead to project cancellation." (Steve McConnell, "Rapid Development", 1996)

"Motivation is undoubtedly the single greatest influence on how well people perform. Most productivity studies have found that motivation has a stronger influence on productivity than any other factor."  (Steve McConnell, "Rapid Development", 1996)

"It's better to wait for a productive programmer to become available than it is to wait for the first available programmer to become productive." (Steve McConnell, "Software Project Survival Guide", 1997)

"Software projects fail for one of two general reasons: the project team lacks the knowledge to conduct a software project successfully, or the project team lacks the resolve to conduct a project effectively." (Steve McConnell, "Software Project Survival Guide", 1997)

"The default movement on a software project should be in the direction of taking elements of the software away to make it simpler rather than adding elements to make it more complex." (Steve McConnell, "Software Project Survival Guide", 1997)

"The job of the average manager requires a shift in focus every few minutes. The job of the average software developer requires that the developer not shift focus more often than every few hours." (Steve McConnell, "Software Project Survival Guide", 1997)

"Trying to apply formal methods to all software projects is just as bad as trying to apply code-and-fix development to all projects." (Steve McConnell, "After the Gold Rush: Creating a True Profession of Software Engineering", 1999)

"A brute force solution that works is better than an elegant solution that doesn't work." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"Building software implies various stages of planning, preparation and execution that vary in kind and degree depending on what's being built." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"Design patterns provide the cores of ready-made solutions that can be used to solve many of software’s most common problems. Some software problems require solutions that are derived from first principles. But most problems are similar to past problems, and those can be solved using similar solutions, or patterns." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"In addition to their complexity-management benefit, design patterns can accelerate design discussions by allowing designers to think and discuss at a larger level of granularity." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"In software, the chain isn't as strong as its weakest link; it's as weak as all the weak links multiplied together." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"Design is heuristic. Dogmatic adherence to any single methodology hurts creativity and hurts your programs." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"On small, informal projects, a lot of design is done while the programmer sits at the keyboard. 'Design' might be just writing a class interface in pseudocode before writing the details. It might be drawing diagrams of a few class relationships before coding them. It might be asking another programmer which design pattern seems like a better choice. Regardless of how it’s done, small projects benefit from careful design just as larger projects do, and recognizing design as an explicit activity maximizes the benefit you will receive from it." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"Simplicity is achieved in two general ways: minimizing the amount of essential complexity that anyone's brain has to deal with at any one time, and keeping accidental complexity from proliferating needlessly." (Steve C McConnell, "Code Complete: A Practical Handbook of Software Construction" 2nd Ed., 2004)

"A good estimate is an estimate that provides a clear enough view of the project reality to allow the project leadership to make good decisions about how to control the project to hit its targets." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"Be sure you understand whether you're presenting uncertainty in an estimate or uncertainty that affects your ability to meet a commitment." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"Don't expect better estimation practices alone to provide more accurate estimates for chaotic projects. You can't accurately estimate an out-of-control process." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"Don't intentionally underestimate. The penalty for underestimation is more severe than the penalty for overestimation. Address concerns about overestimation through planning and control, not by biasing your estimates." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"Not all estimation methods are equal. When looking for convergence or spread among estimates, give more weight to the techniques that tend to produce the most accurate results." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"Treat estimation discussions as problem solving, not negotiation. Recognize that all project stakeholders are on the same side of the table. Everyone wins, or everyone loses." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)

"The primary purpose of software estimation is not to predict a project's outcome; it is to determine whether a project's targets are realistic enough to allow the project to be controlled to meet them." (Steve McConnell, "Software Estimation: Demystifying the Black Art", 2006)