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When to return NULL in PostgreSQL trigger function?
Row-level triggers fired BEFORE can return null to signal the trigger manager to skip the rest of the operation for this row (i.e., subsequent triggers are not fired, and the INSERT / UPDATE / DELETE does not occur for this row). If a nonnull value is returned then the operation proceeds with that row value.
How to create a BEFORE trigger in PostgreSQL?
For this to work you also need to define the trigger as a before trigger: CREATE OR REPLACE FUNCTION test4 () RETURNS TRIGGER AS $BODY$ BEGIN new.vol := new.area * new.alt; RETURN new; END; $BODY$ LANGUAGE plpgsql; CREATE TRIGGER trig_upd BEFORE UPDATE ON “cf” –<< note the BEFORE! FOR EACH ROW EXECUTE PROCEDURE test4 ()
How to create or replace function test4 in PostgreSQL?
CREATE OR REPLACE FUNCTION test4 () RETURNS TRIGGER AS $BODY$ BEGIN new.vol := new.area * new.alt; RETURN new; END; $BODY$ LANGUAGE plpgsql; CREATE TRIGGER trig_upd BEFORE UPDATE ON “cf” –<< note the BEFORE! FOR EACH ROW EXECUTE PROCEDURE test4 () Thanks for contributing an answer to Stack Overflow!
How to use old in when condition for insert and UPDATE triggers?
I need write insert or update trigger, but with WHEN condition with compare OLD and NEW rows. According documentation OLD is null for insert operation. How i can use OLD in WHEN condition for INSERT AND UPDATE triggers? but for insert OLD is null.
What are the data types in PostgreSQL trigger function?
Data type name; the name of the table that caused the trigger invocation. Data type name; the name of the schema of the table that caused the trigger invocation. Data type integer; the number of arguments given to the trigger function in the CREATE TRIGGER statement. Data type array of text; the arguments from the CREATE TRIGGER statement.
When to return the row value of a trigger function?
Returning a row value different from the original value of NEW alters the row that will be inserted or updated. Thus, if the trigger function wants the triggering action to succeed normally without altering the row value, NEW (or a value equal thereto) has to be returned.
Is there context for multi-row update in PostgreSQL?
No row context for multi-row updates – i.e. you’ll have no indication how many rows were altered by some action. No table / schema based filtering – all or nothing will be logged. Information storage is purely text based – possibly need to deal with huge log files where information is all tangled up, and searching is difficult.