InterSystems SQL Reference
NULLIF
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NULLIF(expression1,expression2)
expression1 | An SQL expression. |
expression2 | An SQL expression. |
SQL Function | Comparison Test | Return Value |
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NULLIF(ex1,ex2) | ex1 = ex2 | True returns NULL False returns ex1 |
ISNULL(ex1,ex2) | ex1 = NULL | True returns ex2 False returns ex1 |
IFNULL(ex1,ex2) [two-argument form] | ex1 = NULL | True returns ex2 False returns NULL |
IFNULL(ex1,ex2,ex3) [three-argument form] | ex1 = NULL | True returns ex2 False returns ex3 |
{fn IFNULL(ex1,ex2)} | ex1 = NULL | True returns ex2 False returns ex1 |
NVL(ex1,ex2) | ex1 = NULL | True returns ex2 False returns ex1 |
COALESCE(ex1,ex2,...) | ex = NULL for each argument | True tests next ex argument. If all ex arguments are True (NULL), returns NULL. False returns ex |