# SET_CONSTRAINTS(7) - man - phpman

SET [CONSTRAINTS(7)](https://www.chedong.com/phpMan.php/man/CONSTRAINTS/7/markdown)                 PostgreSQL 14.23 Documentation                 SET [CONSTRAINTS(7)](https://www.chedong.com/phpMan.php/man/CONSTRAINTS/7/markdown)



## NAME
       SET_CONSTRAINTS - set constraint check timing for the current transaction

## SYNOPSIS
       SET CONSTRAINTS { ALL | _name_ [, ...] } { DEFERRED | IMMEDIATE }

## DESCRIPTION
       **SET** **CONSTRAINTS** sets the behavior of constraint checking within the current transaction.
       IMMEDIATE constraints are checked at the end of each statement.  DEFERRED constraints are not
       checked until transaction commit. Each constraint has its own IMMEDIATE or DEFERRED mode.

       Upon creation, a constraint is given one of three characteristics: DEFERRABLE INITIALLY
       DEFERRED, DEFERRABLE INITIALLY IMMEDIATE, or NOT DEFERRABLE. The third class is always
       IMMEDIATE and is not affected by the **SET** **CONSTRAINTS** command. The first two classes start
       every transaction in the indicated mode, but their behavior can be changed within a
       transaction by **SET** **CONSTRAINTS**.

       **SET** **CONSTRAINTS** with a list of constraint names changes the mode of just those constraints
       (which must all be deferrable). Each constraint name can be schema-qualified. The current
       schema search path is used to find the first matching name if no schema name is specified.
       **SET** **CONSTRAINTS** **ALL** changes the mode of all deferrable constraints.

       When **SET** **CONSTRAINTS** changes the mode of a constraint from DEFERRED to IMMEDIATE, the new
       mode takes effect retroactively: any outstanding data modifications that would have been
       checked at the end of the transaction are instead checked during the execution of the **SET**
       **CONSTRAINTS** command. If any such constraint is violated, the **SET** **CONSTRAINTS** fails (and does
       not change the constraint mode). Thus, **SET** **CONSTRAINTS** can be used to force checking of
       constraints to occur at a specific point in a transaction.

       Currently, only UNIQUE, PRIMARY KEY, REFERENCES (foreign key), and EXCLUDE constraints are
       affected by this setting.  NOT NULL and CHECK constraints are always checked immediately when
       a row is inserted or modified (_not_ at the end of the statement). Uniqueness and exclusion
       constraints that have not been declared DEFERRABLE are also checked immediately.

       The firing of triggers that are declared as “constraint triggers” is also controlled by this
       setting — they fire at the same time that the associated constraint should be checked.

## NOTES
       Because PostgreSQL does not require constraint names to be unique within a schema (but only
       per-table), it is possible that there is more than one match for a specified constraint name.
       In this case **SET** **CONSTRAINTS** will act on all matches. For a non-schema-qualified name, once a
       match or matches have been found in some schema in the search path, schemas appearing later
       in the path are not searched.

       This command only alters the behavior of constraints within the current transaction. Issuing
       this outside of a transaction block emits a warning and otherwise has no effect.

## COMPATIBILITY
       This command complies with the behavior defined in the SQL standard, except for the
       limitation that, in PostgreSQL, it does not apply to NOT NULL and CHECK constraints. Also,
       PostgreSQL checks non-deferrable uniqueness constraints immediately, not at end of statement
       as the standard would suggest.



PostgreSQL 14.23                                2026                              SET [CONSTRAINTS(7)](https://www.chedong.com/phpMan.php/man/CONSTRAINTS/7/markdown)