Question

I have a table in SQL Server 2008 which contains custom validation criteria in the form of expressions stored as text, e.g.

StagingTableID    CustomValidation
----------------------------------
1                 LEN([mobile])<=30
3                 [Internal/External] IN ('Internal','External')
3                 ([Internal/External] <> 'Internal') OR (LEN([Contact Name])<=100)
...

I am interested in determining whether all rows in a table pass the conditional statement. For this purpose I am writing a validation stored procedure which checks whether all values in a given field in a given table meet the given condition(s). SQL is not my forte, so after reading this questions this is my first stab at the problem:

EXEC sp_executesql N'SELECT @passed = 0 WHERE EXISTS (' +
                     N'SELECT * FROM (' +
                       N'SELECT CASE WHEN ' + @CustomValidationExpr + N' THEN 1 ' +
                       N'ELSE 0 END AS ConditionalTest ' +
                       N'FROM ' + @StagingTableName +
                     N')t ' +
                     N'WHERE t.ConditionalTest = 0)'
                  ,N'@passed BIT OUTPUT'
                  ,@passed = @PassedCustomValidation OUTPUT

However, I’m not sure if the nested queries can be re-written as one, or if there is an entirely better way for testing for validity of all rows in this scenario?

Thanks in advance!

Answer 1

You should be able to reduce by at least one subquery like this:

EXEC sp_executesql N'SELECT @passed = 0 WHERE EXISTS (' +
                       N'SELECT 1 FROM ' +  @StagingTableName +
                       N'WHERE NOT(' + @CustomValidationExpr + N')) ' +
                  ,N'@passed BIT OUTPUT'
                  ,@passed = @PassedcustomValidation OUTPUT