🛢DBMS: Nondeterministic Function (Definitions)

"A function that may generate different outputs each time it is run, even if the inputs are always the same." (Peter Gulutzan & Trudy Pelzer, "SQL Performance Tuning", 2002)

"A function is non-deterministic if it can return different results when provided with the same input. The RAND function is non-deterministic because it returns a different randomly generated number each time it is called." (Thomas Moore, "EXAM CRAM™ 2: Designing and Implementing Databases with SQL Server 2000 Enterprise Edition", 2005)

"A characteristic of a function that means the function can return different results when provided with the same input. For example, the RAND function is nondeterministic because it returns a different randomly generated number each time it is called." (Thomas Moore, "MCTS 70-431: Implementing and Maintaining Microsoft SQL Server 2005", 2006)

"Nondeterministic functions return different values when they’re invoked with the same arguments." (Joseph L Jorden & Dandy Weyn, "MCTS Microsoft SQL Server 2005: Implementation and Maintenance Study Guide - Exam 70-431", 2006)

"Typically refers to functions such as nondeterministic functions. A nondeterministic function returns different results when called with the same input values. As an example, GETDATE() would return different results at different times. Indexed views can not include nondeterministic functions." (Darril Gibson, "MCITP SQL Server 2005 Database Developer All-in-One Exam Guide", 2008)

"An application whose state of execution cannot be predicted is said to be nondeterministic. Since the operating system schedules threads for execution on processor resources and there are too many factors that influence the OS scheduling, the state of execution of a concurrent application cannot be reliably predicted. Typically, incorrect use of nondeterminism in concurrent applications will be evidenced by the application returning different results from the same inputs." (Clay Breshears, "The Art of Concurrency", 2009)

"Exhibiting a lack of deterministic behavior, so results can vary from run to run of an algorithm. See more in the definition for deterministic." (Michael McCool et al, "Structured Parallel Programming", 2012)

"A user-defined function whose result is not solely dependent on the values of the input arguments. That is, successive invocation with the same argument value can produce a different answer." (Sybase, "Open Server Server-Library/C Reference Manual", 2019)