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IS [ NOT ] DISTINCT FROM

Compares whether two expressions are equal (or not equal). The function is NULL-safe, meaning it treats NULLs as known values for comparing equality. Note that this is different from the EQUAL comparison operator (=), which treats NULLs as unknown values.

Syntax​

<expr1> IS [ NOT ] DISTINCT FROM <expr2>

Returns​

The value returned depends on whether any of the inputs are NULL values:

  • Returns TRUE, if:
    • <null> IS NOT DISTINCT FROM <null>
    • <null> IS DISTINCT FROM <not_null>
    • <not_null> IS DISTINCT FROM <null>
  • Returns FALSE, if:
    • <null> IS DISTINCT FROM <null>
    • <null> IS NOT DISTINCT FROM <not_null>
    • <not_null> IS NOT DISTINCT FROM <null>
  • Otherwise,
    • <expr1> IS DISTINCT FROM <expr2> is equivalent to <expr1> != <expr2>
    • <expr1> IS NOT DISTINCT FROM <expr2> is equivalent to <expr1> = <expr2>
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