![]() ![]() ![]() Referenced Table Schema and Referenced Table Name The constraint is checked only at the end of the transaction. The constraint is checked after each statement. Please check the description of the implementation language of the trigger function about how the trigger arguments are accessible within the function it may be different from normal function arguments. Simple names and numeric constants may be written here, too, but they will all be converted to strings. The arguments are literal string constants. Specify a Boolean WHEN condition, which will be tested to see whether the trigger should be fired.Ī user-supplied function that is declared as taking no arguments and returning type trigger, which is executed when the trigger fires.Īn optional comma-separated list of arguments to be provided to the function when the trigger is executed. Specify the trigger procedure should be fired once for every row affected by the trigger event. Specify the trigger procedure should be fired once per SQL statement. The trigger will only fire if at least one of the listed columns is mentioned as a target of the UPDATE command. The trigger is activated whenever a row is deleted. The trigger is activated whenever a row is modified. The trigger is activated whenever a new row is inserted. The trigger can be specified to fire instead of the operation is attempted on a row.Ĭhoose the events that activate the trigger. The trigger can be specified to fire after the operation is attempted on a row. The trigger can be specified to fire before the operation is attempted on a row. Note: Support from PostgreSQL 9.0 or later. Click -> Trigger to open an object list for Trigger.Ĭheck this box to create a constraint trigger.Ĭhoose the type of the trigger: Table or View. PostgreSQL supports row-level and statement-level triggers.Triggers are database operations that are automatically performed when a specified database event occurs.A trigger is a function invoked automatically when an INSERT, UPDATE, DELETE, or TRUNCATE occurs on a table.PostgreSQL requires you to define a user-defined function as the action of the trigger, while the SQL standard allows you to use any SQL commands.PostgreSQL allows you to define the statement-level trigger on views.PostgreSQL fires trigger for the TRUNCATE event. ![]() PostgreSQL triggers vs SQL standard triggersĮven though PostgreSQL implements SQL standard, triggers in PostgreSQL has some specific features: The main drawback of using a trigger is that you must know the trigger exists and understand its logic to figure out the effects when data changes. For example, when a new row is added into the customer table, other rows must be also created in tables of banks and credits. For example, if you want to keep the history of data without requiring the application to have logic to check for every event such as INSERT or UDPATE.Īlso, you can use triggers to maintain complex data integrity rules which cannot implement elsewhere except at the database level. Triggers are useful in case the database is accessed by various applications, and you want to keep the cross-functionality within the database that runs automatically whenever the data of the table is modified. In case the trigger is invoked after the event, all changes are available to the trigger. ![]() If the trigger is invoked before an event, it can skip the operation for the current row or even change the row being updated or inserted. You can specify whether the trigger is invoked before or after an event. The differences between the two kinds are how many times the trigger is invoked and at what time.įor example, if you issue an UPDATE statement that modifies 20 rows, the row-level trigger will be invoked 20 times, while the statement-level trigger will be invoked 1 time. PostgreSQL provides two main types of triggers: The difference between a trigger and a user-defined function is that a trigger is automatically invoked when a triggering event occurs. To create a new trigger, you define a trigger function first, and then bind this trigger function to a table. An event could be any of the following: INSERT, UPDATE, DELETE or TRUNCATE.Ī trigger is a special user-defined function associated with a table. What are PostgreSQL triggersĪ PostgreSQL trigger is a function invoked automatically whenever an event associated with a table occurs. Summary: in this tutorial, you will learn about PostgreSQL triggers, why you should use the triggers, and when to use them. ![]()
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