<=> (Spaceship operator)

1. Supports is not distinct from

The not standardized spaceship operator (<=>) works in some SQL dialects like a null-safe comparison: It is similar to = but never returns unknown. Instead it returns false if only one argument is null or true if both arguments are null.

SELECT …
  FROM …
 WHERE c1 <=> c2

Note that this is not a three-way comparison in the way PHP or C++ use the spaceship operator.

Related

• Standardised version of this operator: IS NOT DISTINCT FROM (null-safe equals comparison)

• Tutorials:

  • NULL-Aware Comparison: is [not] distinct from (with further alternatives)

  • NULL: Indicating the Absence of Data

  • The Three-Valued Logic of SQL

Normative References

<=> is not defined in the SQL standard.