Wiki / Configuration Parameters

When on, expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL, that is, they return true if expr evaluates to the null value, and false otherwise. The correct SQL-spec-compliant behavior of expr = NULL is to always return null (unknown). Therefore this parameter defaults to off. However, filtered forms in Microsoft Access generate queries that appear to use expr = NULL to test for null values, so if you use that interface to access the database you might want to turn this option on. Since expressions of the form expr = NULL always return the null value (using the SQL standard interpretation), they are not very useful and do not appear often in normal applications so this option does little harm in practice. But new users are frequently confused about the semantics of expressions involving null values, so this option is off by default. Note that this option only affects the exact form = NULL, not other comparison operators or other expressions that are computationally equivalent to some expression involving the equals operator (such as IN). Thus, this option is not a general fix for bad programming. Refer to Section 9.2 for related information.

English manual coverage begins with PostgreSQL 7.4. Source history and runtime observations have their own recorded version boundaries.

boot val

off

category

Version and Platform Compatibility / Other Platforms and Clients

context

user

documented

true

enumvals

Unknown

lang

en

max val

Unknown

metadata version

18

min val

Unknown

name

transform_null_equals

short desc

Treats "expr=NULL" as "expr IS NULL".

source

pg-settings-source-snapshot

unit

Unknown

vartype

bool

When turned on, expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL, that is, they return true if expr evaluates to the null value, and false otherwise. The correct behavior of expr = NULL is to always return null (unknown).