Editing PostgreSQL (section)

=== Triggers ===
Triggers are events triggered by the action of SQL [[data manipulation language]] (DML) statements. For example, an [[Insert (SQL)|INSERT]] statement might activate a trigger that checks if the values of the statement are valid. Most triggers are only activated by either INSERT or [[Update (SQL)|UPDATE]] statements.

Triggers are fully supported and can be attached to tables. Triggers can be per-column and conditional, in that UPDATE triggers can target specific columns of a table, and triggers can be told to execute under a set of conditions as specified in the trigger's WHERE clause. Triggers can be attached to [[View (SQL)|views]] by using the INSTEAD OF condition. Multiple triggers are fired in alphabetical order. In addition to calling functions written in the native PL/pgSQL, triggers can also invoke functions written in other languages like PL/Python or PL/Perl.