🔏MS Office: Excel for SQL Developers IV (Differences Between Two Datasets)

    One of the tasks which appears from time to time on my table is to determine the differences between two datasets coming from different systems or from the same system/source but taken at different points in time. Even if it’s fairly simple to write such a query, especially when the number of attributes is quite small, there is lot of repetitive work that needs to be done because typically for each set of matched attributes needs to be added a third attribute (difference flag) showing whether there is a difference or not. In time I started to use Excel formulas to create the SELECT clause for such a query, matching tables’ attribute first and categorizing the data types mainly in 4 categories: text, amounts, numeric (other than amounts) and dates. This categorization is requested first of all by the different ways in handling the NULL values for each data type, and secondly by the difference between amounts and numeric, even if they might have the same data type, the difference resides in the fact that amounts might be rounded differently in each data source, therefore a difference of a few cents will not be considered as difference.

    Given two attributes ColumnX and ColumnY from tables A, respectively B, let’s look first on how the difference flag constraint could be written for each category:

--text attributes: 
CASE 
    WHEN IsNull(A.ColumnX , '')<> ISNULL(B.ColumnY, '') THEN 'Y' 
    ELSE 'N' 
END DiffColumnXYFlag 

--amount attributes: 
CASE 
    WHEN IsNull(A.ColumnX, 0) - IsNull(B.ColumnY, 0) NOT BETWEEN -0.05 AND 0.05 THEN 'Y' 
    ELSE 'N' 
END DiffColumnXYFlag 

--numeric attributes: 
CASE 
    WHEN IsNull(A.ColumnX, 0) <> IsNull(B.ColumnY, 0) THEN 'Y' 
    ELSE 'N' 
END DiffColumnXYFlag 

--date attributes: 
CASE 
   WHEN IsNull(DateDiff(d, A.ColumnX, B.ColumnY), -1)<>0 THEN 'Y' 
   ELSE 'N' 
END DiffColumnXYFlag 

Notes:
1.   Bit attributes can be treated as numeric as long as they are considered as having a bi-state, for tri-state values in which also NULL is considered as a distinct value then the constraint must be changed, the most natural way being to translate the NULL to –1:
CASE
    WHEN IsNull(A.ColumnX, -1) <> IsNull(B.ColumnY, -1) THEN 'Y'
    ELSE 'N'
END DiffColumnXYFlag
2.   In most of the examples I worked with the difference between two pair dates, the difference was calculated at day level, though it might happen that is needed to compare the values at smaller time intervals to the order of hours, minutes or seconds. The only thing that needs to be changed then is the first parameter from DateDiff function. There could be also situations in which a difference of several seconds is acceptable, a BETWEEN operator could be used then as per the case of numeric vs. amount values.
3.    In case one of the attributes is missing, the corresponding difference flag could take directly the value ‘N’ or ‘n/a’.
4.   It could happen that there are mismatches between the attributes’ data type, in this case at least one of them must be converted to a form that could be used in further processing.

    Thus a macro for this purpose would take as input a range with the list of attributes from the two tables, the data type category and the columns participating in the join constraint, two parameters designating the name of the left and right table participating in the FULL OUTER JOIN, the time interval considered, the error margin value interval (e.g. [-e, e]) and a flag indicating whether to show all combined data or only the records for which there is at least a difference found. 

Function GetComparisonQuery(ByVal rng As Range, ByVal LeftTable As String, ByVal RightTable As String, ByVal TimeInterval As String, ByVal ErrorMargin As String, ByVal ShowOnlyDifferencesFlag As Boolean) As String 
'builds the code for a comparison query between two tables 
Dim attributes As String 
Dim differences As String 
Dim constraint As String 
Dim whereConstraints As String 
Dim joinConstraints As String 
Dim columnX As String 
Dim columnY As String 
Dim index As Integer 
For index = 1 To rng.Rows.Count 
    columnX = Trim(rng.Cells(index, 1).Value) 
    columnY = Trim(rng.Cells(index, 2).Value) 
  
    If Len(columnX) > 0 Or Len(columnY) > 0 Then 
       If Len(columnX) > 0 Then 
            attributes = attributes & ", A." & columnX & " LT" & columnX & vbCrLf 
       End If 
       If Len(columnY) > 0 Then 
            attributes = attributes & ", B." & columnY & " RT" & columnX & vbCrLf 
       End If 
       
       constraint = "" 
       If Len(Trim(rng.Cells(index, 4).Value)) = 0 Then 
            If Len(columnX) > 0 And Len(columnY) > 0 Then 
                 'creating the difference flag 
                 Select Case Trim(rng.Cells(index, 3).Value) 
                 Case "text": 
                      constraint = "CASE" & vbCrLf & _ 
                                   "     WHEN IsNull(A." & columnX & " , '') <> IsNUll(B." & columnY & ", '') THEN 'Y'" & vbCrLf & _ 
                                   "     ELSE 'N'" & vbCrLf & _ 
                                   "  END" 
                 Case "amount": 
                      constraint = "CASE" & vbCrLf & _ 
                                   "     WHEN IsNull(A." & columnX & " , 0) - IsNUll(B." & columnY & ", 0) NOT BETWEEN -" & ErrorMargin & " AND " & ErrorMargin & " THEN 'Y'" & vbCrLf & _ 
                                   "     ELSE 'N'" & vbCrLf & _ 
                                   "  END" 
                 Case "numeric": 
                      constraint = "CASE" & vbCrLf & _ 
                                   "     WHEN IsNull(A." & columnX & " , 0) <> IsNUll(B." & columnY & ", 0) THEN 'Y'" & vbCrLf & _ 
                                   "     ELSE 'N'" & vbCrLf & _ 
                                   "  END" 
                 Case "date": 
                      constraint = "CASE" & vbCrLf & _ 
                                   "     WHEN DateDiff(" & TimeInterval & ", A." & columnX & ", B." & columnY & ")<>0 THEN 'Y'" & vbCrLf & _ 
                                   "     ELSE 'N'" & vbCrLf & _ 
                                   "  END" 
                 Case Else: 'error 
                     MsgBox "Incorrect data type provided for " & index & " row!", vbCritical 
                 End Select 
                 
                
                If ShowOnlyDifferencesFlag Then 
                   whereConstraints = whereConstraints & " OR " & constraint & " = 'Y'" & vbCrLf 
                End If 
                
                differences = differences & ", " & constraint & " Diff" & columnX & "Flag" & vbCrLf 
            Else 
                differences = differences & ", 'n/a' Diff" & IIf(Len(columnX) > 0, columnX, columnY) & "Flag" & vbCrLf 
            End If 
                             
        Else 
            joinConstraints = joinConstraints & "    AND A." & columnX & " = B." & columnY & vbCrLf 
        End If 
     
     End If 
Next 
If Len(attributes) > 0 Then 
    attributes = Right(attributes, Len(attributes) - 2) 
End If 
If Len(joinConstraints) > 0 Then 
    joinConstraints = Right(joinConstraints, Len(joinConstraints) - 8) 
End If 
If Len(whereConstraints) > 0 Then 
    whereConstraints = Right(whereConstraints, Len(whereConstraints) - 4) 
End If 
'building the comparison query 
GetComparisonQuery = "SELECT " & attributes & _ 
    differences & _ 
    "FROM " & LeftTable & " A" & vbCrLf & _ 
    "     FULL OUTER JOIN " & RightTable & " B" & vbCrLf & _ 
    "       ON " & joinConstraints & _ 
    IIf(ShowOnlyDifferencesFlag And Len(whereConstraints) > 0, "WHERE " & whereConstraints, "") 
   
End Function 

 



    The query returned by the macro for the above example based on attributes from Production.Product table from AdventureWorks database and Production.Products table created in Saving Data With Stored Procedures post: 

 

SELECT A.ProductID LTProductID 
, B.ProductID RTProductID 
, A.Name LTName 
, B.Name RTName 
, A.ProductNumber LTProductNumber 
, B.ProductNumber RTProductNumber 
, A.MakeFlag LTMakeFlag 
, B.MakeFlag RTMakeFlag 
, A.FinishedGoodsFlag LTFinishedGoodsFlag 
, B.FinishedGoodsFlag RTFinishedGoodsFlag 
, A.Color LTColor 
, B.Color RTColor 
, A.SafetyStockLevel LTSafetyStockLevel 
, B.SafetyStockLevel RTSafetyStockLevel 
, A.ReorderPoint LTReorderPoint 
, A.StandardCost LTStandardCost 
, B.StandardCost RTStandardCost 
, A.ListPrice LTListPrice 
, B.ListPrice RTListPrice 
, A.Size LTSize 
, A.DaysToManufacture LTDaysToManufacture 
, A.ProductLine LTProductLine 
, A.Class LTClass 
, A.Style LTStyle 
, A.SellStartDate LTSellStartDate 
, B.StartDate RTSellStartDate 
, A.SellEndDate LTSellEndDate 
, B.EndDate RTSellEndDate 
, A.DiscontinuedDate LTDiscontinuedDate 
, B.CreationDate RT 
, B.CreatedBy RT 
, A.ModifiedDate LTModifiedDate 
, B.ModifiedDate RTModifiedDate 
, B.ModifiedBy RT 
, CASE 
    WHEN IsNull(A.Name , '') <> IsNUll(B.Name, '') THEN 'Y' 
    ELSE 'N' 
END DiffNameFlag 
, CASE 
    WHEN IsNull(A.ProductNumber , '') <> IsNUll(B.ProductNumber, '') THEN 'Y' 
    ELSE 'N' 
END DiffProductNumberFlag 
, CASE 
    WHEN IsNull(A.MakeFlag , 0) <> IsNUll(B.MakeFlag, 0) THEN 'Y' 
    ELSE 'N' 
END DiffMakeFlagFlag 
, CASE 
    WHEN IsNull(A.FinishedGoodsFlag , 0) <> IsNUll(B.FinishedGoodsFlag, 0) THEN 'Y' 
    ELSE 'N' 
END DiffFinishedGoodsFlagFlag 
, CASE 
     WHEN IsNull(A.Color , '') <> IsNUll(B.Color, '') THEN 'Y' 
    ELSE 'N' 
END DiffColorFlag 
, CASE 
    WHEN IsNull(A.SafetyStockLevel , 0) <> IsNUll(B.SafetyStockLevel, 0) THEN 'Y' 
    ELSE 'N' 
END DiffSafetyStockLevelFlag 
, 'n/a' DiffReorderPointFlag 
, CASE 
     WHEN IsNull(A.StandardCost , 0) - IsNUll(B.StandardCost, 0) NOT BETWEEN -0.05 AND 0.05       
     THEN 'Y' 
ELSE 'N' 
END DiffStandardCostFlag 
, CASE 
     WHEN IsNull(A.ListPrice , 0) - IsNUll(B.ListPrice, 0) NOT BETWEEN -0.05 AND 0.05 THEN 'Y' 
     ELSE 'N' 
END DiffListPriceFlag 
, 'n/a' DiffSizeFlag 
, 'n/a' DiffDaysToManufactureFlag 
, 'n/a' DiffProductLineFlag 
, 'n/a' DiffClassFlag 
, 'n/a' DiffStyleFlag 
, CASE 
    WHEN DateDiff(d, A.SellStartDate, B.StartDate)<>0 THEN 'Y' 
    ELSE 'N' 
END DiffSellStartDateFlag 
, CASE 
    WHEN DateDiff(d, A.SellEndDate, B.EndDate)<>0 THEN 'Y' 
    ELSE 'N' 
END DiffSellEndDateFlag 
, 'n/a' DiffDiscontinuedDateFlag 
, 'n/a' DiffCreationDateFlag 
, 'n/a' DiffCreatedByFlag 
, CASE 
     WHEN DateDiff(d, A.ModifiedDate, B.ModifiedDate)<>0 THEN 'Y' 
     ELSE 'N' 
END DiffModifiedDateFlag 
, 'n/a' DiffModifiedByFlag 
FROM Production.Product A 
    FULL OUTER JOIN Production.Products B 
       ON A.ProductID = B.ProductID 
WHERE CASE 
     WHEN IsNull(A.Name , '') <> IsNUll(B.Name, '') THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
    WHEN IsNull(A.ProductNumber , '') <> IsNUll(B.ProductNumber, '') THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
     WHEN IsNull(A.MakeFlag , 0) <> IsNUll(B.MakeFlag, 0) THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
     WHEN IsNull(A.FinishedGoodsFlag , 0) <> IsNUll(B.FinishedGoodsFlag, 0) THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
     WHEN IsNull(A.Color , '') <> IsNUll(B.Color, '') THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
     WHEN IsNull(A.SafetyStockLevel , 0) <> IsNUll(B.SafetyStockLevel, 0) THEN 'Y' 
     ELSE 'N' 
END = 'Y' 
OR CASE 
     WHEN IsNull(A.StandardCost , 0) - IsNUll(B.StandardCost, 0) NOT BETWEEN -0.05 AND 0.05 
      THEN 'Y' 
ELSE 'N' 
END = 'Y' 
OR CASE 
      WHEN IsNull(A.ListPrice , 0) - IsNUll(B.ListPrice, 0) NOT BETWEEN -0.05 AND 0.05 THEN 'Y' 
      ELSE 'N' 
END = 'Y' 
OR CASE 
      WHEN DateDiff(d, A.SellStartDate, B.StartDate)<>0 THEN 'Y' 
      ELSE 'N' 
END = 'Y' 
OR CASE 
      WHEN DateDiff(d, A.SellEndDate, B.EndDate)<>0 THEN 'Y' 
      ELSE 'N' 
END = 'Y' 
OR CASE 
       WHEN DateDiff(d, A.ModifiedDate, B.ModifiedDate)<>0 THEN 'Y' 
      ELSE 'N' 
END = 'Y' 

Notes:
1.   The macro doesn’t consider an ORDER BY clause, though it could be easily added manually
2.   Not all of the join constraints are so simple so that they can be reduced to one or more simple equalities, on the other side we have to consider that the most time consuming task is listing the attributes and the difference flags.
3.    Sometimes it’s easier to create two extracts – in the first being considered all the records from the left table and the matches from the right table (left join), respectively all the records from the right table and the matches from the left table (right join).
4.     Given the fact that the attributes participating in the join clause should in theory match, each pair of such attributes could be merged in one attribute using the formula: IsNull(A.ColumnX, B.ColumnY) As ColumnXY.
5.     In order to show all the data from the two tables and not only the differences, all is needed to do is to change the value of the last parameter from true to false:
=GetComparisonQuery(A2:D23, "Production.Product", "Production.Products", "d", "0.05", false) 
6.     For TimeInterval parameter should be provided only the values taken by DatePart parameter (first parameter) of SQL Server’s DateDiff function.
7.     Please note that no validation is made for the input parameters.

🔏MS Office: Excel for SQL Developers III (Creating a Stored Procedure from Table’s Metadata)

In a previous post I was showing a simple technique for using stored procedures for inserting/updating data within SQL Server 2005+. From a rough estimation I think that about 80% of the stored procedures built for this purpose could use the same template, without including additional business logic. Given the fact that databases store metadata about their objects, table’s metadata could be used to create such a stored procedure using VBA or more complex programming languages. SQL Server 2008 stores its table’s columns metadata in INFORMATION_SCHEMA.COLUMNS view, the required information for the Products created in the previous post could be get using the following query:

-- SQL Server 2008 Table/Column Metadata SELECT TABLE_SCHEMA SchemaName 
, TABLE_NAME TableName 
, COLUMN_NAME ColumnName 
, DATA_TYPE DataType 
, CHARACTER_MAXIMUM_LENGTH Length 
, IS_NULLABLE IsNullable 
, NUMERIC_PRECISION Precision 
, NUMERIC_SCALE NumericScale 
FROM INFORMATION_SCHEMA.COLUMNS 
WHERE TABLE_NAME = 'Products' 
ORDER BY TABLE_NAME 
, ORDINAL_POSITION 

The output of the above query could be easily copy-pasted into Excel or directly exported using the SQL Server Import and Export Wizard, the range with data (without headers) being passed as parameter to GetStoredProcedure macro created for this post together with stored procedure and table’s name.

 

Macro’s construction is based on the following presumptions:
1.   The first attribute in the target table is always table’s primary key.
2.   The stored procedure considers only simple data types though it can be extended to support further data types.
3.   Stored procedure's name and table's name contains also the schemas in which the respective objects are created.
4.   CreationDate, ModifiedDate, CreatedBy and ModifiedBy are reserved words for tracking the timestamp and the User who created/modified the record.
5.   The UserID  will be the last parameter in case the CreatedBy or ModifiedBy are in scope.

And here’s the macro GetStoredProcedure with its afferent Metadata Enumeration that maps the column order from the above query, and the GetDataType function that translates the metadata related to data type to the actual parameters’ data type: 

 

Enum Metadata 
  enmSchemaName = 1 
  enmTableName = 2 
  enmColumnName = 3 
  enmDataType = 4 
  enmLength = 5 
  enmIsNullable = 6 
  enmPrecision = 7 
  enmNumericScale = 8 
End Enum 

Function GetStoredProcedure(ByVal rng As Range, ByVal ProcedureName As String, ByVal TableName As String) As String 
'builds the code for a stored procedure based on table's metadata 
Dim parameters As String 
Dim columnName As String 
Dim parameterName As String 
Dim columnValue As String 
Dim insert As String 
Dim columns As String 
Dim update As String 
Dim indexRow As Integer 
Dim ID As String 
Dim insertUserID As Boolean 

insertUserID = False 

For index = 1 To rng.Rows.Count 
    If Len(Trim(Cells(index, Metadata.enmTableName).Value)) > 0 And Len(Trim(Cells(index, Metadata.enmColumnName))) Then 
       'translating column names 
       Select Case rng.Cells(index, Metadata.enmColumnName) 
       Case "CreationDate": 
            columnName = "" 
            columnValue = "GetDate()" 
            parameterName = "" 
       Case "ModifiedDate": 
            columnName = "ModifiedDate" 
            columnValue = "GetDate()" 
            parameterName = "" 
       Case "CreatedBy": 
            columnName = "" 
            columnValue = "@UserID" 
            parameterName = "" 
            insertUserID = True 
       Case "ModifiedBy": 
            columnName = Trim(rng.Cells(index, Metadata.enmColumnName)) 
            columnValue = "@UserID" 
            parameterName = "" 
            insertUserID = True 
       Case Else: 
            columnName = Trim(rng.Cells(index, Metadata.enmColumnName)) 
            columnValue = "@" & columnName 
            parameterName = "@" & columnName 
       End Select 
       
       If index = 1 Then 
            ID = columnName 
       Else 
            columns = columns & ", " & Trim(rng.Cells(index, Metadata.enmColumnName)) 
            insert = insert & ", " & columnValue 
            
            If Len(columnName) > 0 Then 
                 update = update & Space(9) & ", " & columnName & " = " & columnValue & "" & vbCrLf 
            End If 
       End If 
       
        If Len(parameterName) > 0 Then 
             parameters = parameters & ", " & parameterName & " " & GetDataType(Trim(rng.Cells(index, Metadata.enmDataType).Value), Trim(rng.Cells(index, Metadata.enmLength).Value), Trim(rng.Cells(index, Metadata.enmPrecision).Value), Trim(rng.Cells(index, Metadata.enmNumericScale).Value)) & vbCrLf 
         End If 
    End If 
Next 

If Len(columns) > 0 Then 
    columns = Right(columns, Len(columns) - 1) 
End If 
If Len(insert) > 0 Then 
    insert = Right(insert, Len(insert) - 1) 
End If 
If Len(update) > 0 Then 
    update = Right(update, Len(update) - 10) 
End If 
If Len(parameters) > 0 Then 
    parameters = Right(parameters, Len(parameters) - 1) & IIf(insertUserID, ", @UserID int" & vbCrLf, "") 
End If 

'building the stored procedure string 
GetStoredProcedure = "CREATE PROCEDURE " & ProcedureName & "(" & vbCrLf & parameters & ")" & vbCrLf & _ 
    "AS" & vbCrLf & _ 
    "BEGIN" & vbCrLf & _ 
    "BEGIN TRY" & vbCrLf & _ 
    "    IF ISNULL(@" & ID & ", 0) = 0" & vbCrLf & _ 
    "    BEGIN" & vbCrLf & _ 
    "    -- insert statement" & vbCrLf & _ 
    "       INSERT INTO " & TableName & " (" & columns & ")" & vbCrLf & _ 
    "       VALUES (" & insert & ")" & vbCrLf & _ 
    "       SET @" & ID & " = @@IDENTITY" & vbCrLf & _ 
    "    END" & vbCrLf & _ 
    "    ELSE" & vbCrLf & _ 
    "    BEGIN" & vbCrLf & _ 
    "        -- update statement" & vbCrLf & _ 
    "        UPDATE " & TableName & vbCrLf & _ 
    "        SET " & update & _ 
    "        WHERE " & ID & "= @" & ID & vbCrLf & _ 
    "    END" & vbCrLf & _ 
    "    SELECT @" & ID & vbCrLf & _ 
    "END TRY" & vbCrLf & _ 
    "BEGIN CATCH" & vbCrLf & _ 
    "   SELECT Cast(ERROR_NUMBER() as varchar(10)) + ':' + ERROR_MESSAGE()" & vbCrLf & _   
    "END CATCH" & vbCrLf & _ 
    "END" 

End Function 

Private Function GetDataType(ByVal DataType As String, ByVal Length As String, ByVal NumericPrecision As String, ByVal NumericScale As String) As String 
'translating data types 
Select Case DataType 
    Case "varchar": GetDataType = DataType & "(" & Length & ")" 
    Case "nvarchar": GetDataType = DataType & "(" & Length & ")" 
    Case "nchar": GetDataType = DataType & "(" & Length & ")" 
    Case "decimal": GetDataType = DataType & "(" & NumericPrecision & "," & NumericScale & ")" 
    Case "numeric": GetDataType = DataType & "(" & NumericPrecision & "," & NumericScale & ")" 
    Case "money": GetDataType = DataType & "(" & NumericPrecision & "," & NumericScale & ")" 
    Case "smallmoney": GetDataType = DataType & "(" & NumericPrecision & "," & NumericScale & ")" 
    Case Else: GetDataType = DataType 
End Select 

End Function 

Note:
As always, there is enough place for improvement, I just tried to exemplify the utility of such a function that could reduce considerably developers’ time for building such stored procedures.

💎SQL Reloaded: Saving Data With Stored Procedures

    Without going too much into details on the benefits of stored procedures, in this post I will show a simple technique I usually like to use for database updates. It’s not rocket science, I bet many of the developers use similar approaches, and many more don’t! Stored procedures are the ideal place for storing your business logic, including insert/updates, in addition stored procedures being recommended as a way of avoiding SQL injection and facilitate code’s maintenance. Doing inserts/updates in a stored procedure implies sending each attribute that needs to be maintain, and given the fact that, with small exceptions, the same parameters are sent, it makes sense to bring the two statements in the same stored procedure. The difference in the number of parameters resides actually in the Primary Key which is sent in the update case in order to identify uniquely the record that needs to be updated, though this fact could be used to determine whether is dealt with an insert or an update.

   Enough with the talking, so let’s consider the below table in which a unique constrain is defined on ProductNumber attribute: 

 

CREATE TABLE Production.Products( 
ProductID int IDENTITY(1,1) NOT NULL, 
Name nvarchar(250) NOT NULL, 
ProductNumber nvarchar(25) NOT NULL, 
MakeFlag bit NOT NULL, 
FinishedGoodsFlag bit NOT NULL, 
Color nvarchar(15) NULL, 
SafetyStockLevel int NULL, 
ListPrice decimal(13,2) NOT NULL, 
StandardCost decimal(13,2) NOT NULL, 
CreationDate smalldatetime NOT NULL, 
CreatedBy int NOT NULL, 
ModifiedDate smalldatetime NOT NULL, 
ModifiedBy int NOT NULL) 

    The table is based on Production.Product table from AdventureWorks database, however I reduced the number of attributes and simplified table’s definition. I introduced also the Creation/Modified Dates used as timestamps for the creation/modification of a record, and the Created/Modified By as a reference to the User that performed the respective actions. From all these 4 attributes is enough to send only the User ID, the actual timestamp being obtained using the GetDate function in the background, so we’ll have in the end 13-3= 10 parameters. Here is the stored procedure: 

 

CREATE PROCEDURE dbo.pUpdateProducts( 
  @ProductID int 
, @Name nvarchar(250) 
, @ProductNumber nvarchar(25) 
, @MakeFlag bit 
, @FinishedGoodsFlag bit 
, @Color nvarchar(15) 
, @SafetyStockLevel int 
, @ListPrice decimal(13,2) 
, @StandardCost decimal(13,2) 
, @StartDate smalldatetime 
, @EndDate smalldatetime 
, @UserID int) 
AS 
BEGIN 
BEGIN TRY 
    IF ISNULL(@ProductID, 0) = 0 
    BEGIN 
        -- insert statement 
        INSERT INTO Production.Products (Name, ProductNumber, MakeFlag, FinishedGoodsFlag, Color , SafetyStockLevel 
, ListPrice, StandardCost, StartDate, EndDate, CreationDate, CreatedBy, ModifiedDate, ModifiedBy) 
        VALUES ( @Name, @ProductNumber, IsNull(@MakeFlag, 0), IsNull(@FinishedGoodsFlag, 0), @Color , @SafetyStockLevel 
, @ListPrice, @StandardCost, @StartDate, @EndDate, GETDATE(), @UserID, GETDATE(), @UserID) 
        SET @ProductID = @@IDENTITY 
     END 
     ELSE 
     BEGIN 
          -- update statement 
          UPDATE Production.Products 
          SET Name = @Name 
         , ProductNumber = @ProductNumber 
         , MakeFlag = IsNull(@MakeFlag, 0)  
         , FinishedGoodsFlag = IsNull(@FinishedGoodsFlag, 0) 
         , Color = @Color 
         , SafetyStockLevel = @SafetyStockLevel 
         , ListPrice = @ListPrice 
         , StandardCost = @StandardCost 
        , StartDate = @StartDate 
        , EndDate = @EndDate 
        , ModifiedDate = GETDATE() 
        , ModifiedBy = @UserID 
        WHERE ProductID = @ProductID 
     END 
     SELECT @ProductID 
END TRY 
BEGIN CATCH 
     SELECT Cast(ERROR_NUMBER() as varchar(10)) + ':' + ERROR_MESSAGE() 
END CATCH 
END 

    The TRY… CATCH… block introduced with SQL Server 2005 allows trapping the errors and thus returns error details to the calling application. In case the DML statement succeeded is returned the Primary Key of the just updated, respectively inserted record. Let’s see the stored procedure in action: 

--inserting new records    
EXEC dbo.pUpdateProducts 0, 'Product 1', 'Product1', 1, 1, 'Blue', 100, 50.32 , 44.06, '2010-01-01', NULL, 1 -- Example 1 
EXEC dbo.pUpdateProducts 0, 'Product 2', 'Product2', 0, 1, 'Red', 100, 51.32 , 44.45, '2010-01-01', NULL, 1 -- Example 2 
EXEC dbo.pUpdateProducts 0, 'Product 3', 'Product3', 1, 0, 'Gren', 100, 59.32 , 44.87, '2010-01-01', NULL, 1 -- Example 3 
EXEC dbo.pUpdateProducts 0, 'Product 4', 'Product4', 0, 0, 'Red', 100, 57.32 , 44.78, '2010-01-01', NULL, 1 -- Example 4 

    After running the above EXEC statements try to run them again, each of them will error out with the following error details: 2601:Cannot insert duplicate key row in object 'Production.Products' with unique index 'IX_Products_UniqueProductNumber'. It will be in developer’s attribution to translate the error to a more appealing error message.

    In order to update a record all is needed to do is to transmit the ID of the record to be updated and the new values. For example in a new created table the record created by first example will more likely correspond to ProductID = 1, thus the following statement is used to change its values: 

 

-- updating a record 
EXEC dbo.pUpdateProducts 1, 'Product 1', 'Product1', 1, 1, 'White', 100, 50.32 , 44.06, '2010-01-01', NULL, 1 -- Example 1 

Note:
    This technique has the inconvenience that it doesn’t consider the cases in which two different Users update the same record, though that’s a topic for another post.