SQL Server/T-SQL Tutorial/Data Convert Functions/NULLIF
Returning a NULL Value When Two Expressions Are Equal: Otherwise Return the First Expression
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5> DECLARE @Value1 int 6> DECLARE @Value2 int 7> SET @Value1 = 55 8> SET @Value2 = 955 9> SELECT NULLIF(@Value1, @Value2) 10> GO
55
(1 rows affected) 1> 2> 3> DECLARE @Value1 int 4> DECLARE @Value2 int 5> SET @Value1 = 55 6> SET @Value2 = 55 7> SELECT NULLIF(@Value1, @Value2) 8> GO
NULL
(1 rows affected) 1></source>