Thursday, November 10, 2011

Deterministic Functions and Nondeterministic Functions

Deterministic functions: always returns the same output result all the time it is executed for same input values.
             Exp: ABS, DATEDIFF, ISNULL etc.
Nondeterministic functions: may return different results each time they are executed. 
             Exp: NEWID, RAND, @@CPU_BUSY etc. 
Functions that call extended stored procedures are nondeterministic. User-defined functions that create side effects on the database are not recommended.

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