IS DISTINCT FROM (null-safe not equals comparison)

1. Supports the non-standard spaceship operator instead: <=>
2. Supports the non-standard binary is operator instead
3. Not for row-values

The not-equals comparison (<>) returns unknown if one of the compared values is the null value. Is distinct from is similar to <> except that it never returns unknown. Instead it returns true if only one argument is null or false if both arguments are null.

SELECT …
  FROM …
 WHERE c1 IS DISTINCT FROM c2

Related

• Negation: IS NOT DISTINCT FROM (null-safe equals comparison)

• Tutorials:

  • NULL-Aware Comparison: is [not] distinct from

  • NULL: Indicating the Absence of Data

  • The Three-Valued Logic of SQL

Normative References

Is distinct from is defined in ISO/IEC 9075-2:2023 as the optional feature T151, “DISTINCT predicate”.