In today’s article, we will learn A PostgreSQL trigger is a database object that automatically executes a function in response to an event such as insert, update, delete, or truncate.<\/p>\n
Triggers cannot be operated manually by users.<\/p>\n
Triggers perform actions before or after the action is taken, according to the actions written in them.<\/p>\n
Triggers cause performance loss in DML operations coming to the table in which they are located.<\/p>\n
Triggers can cause locks on large data.<\/p>\n
After Trigger:<\/strong> Triggers that come into play after the transaction takes place.<\/p>\n Before Trigger:<\/strong> It is the trigger that comes into play after the transaction takes place.<\/p>\n Instead Of Trigger:<\/strong> Used while the action is about to take place.<\/p>\n FOR EACH ROW:<\/strong> It is done for every transaction made. For example, if 1000 deletes were made, it writes them all.<\/p>\n FOR EACH STATEMENT:<\/strong> Performs a single transaction for each transaction made. For example, if 1000 deletes are made, only one will be written.<\/p>\n To define a trigger in PostgreSQL, we first need to create a function or procedure for the desired operation. After doing this, we need to specify the function or procedure created in the trigger.<\/p>\nIts general usage is as follows.<\/h4>\n
CREATE FUNCTION trigger_function() \r\n RETURNS TRIGGER \r\n LANGUAGE PLPGSQL\r\nAS $$\r\nBEGIN\r\n -- trigger logic\r\nEND;\r\n$$\r\n\r\nCREATE TRIGGER trigger_ismi\r\n AFTER INSERT\r\n ON tablo_adi\r\n FOR EACH ROW\r\n EXECUTE PROCEDURE function_ismi();<\/pre>\n