Module Structure

PSQL code modules consist of a header and a body.The DDL statements for defining them are complex statements;that is, they consist of a single statement that encloses blocks of multiple statements.These statements begin with a verb (CREATE, ALTER, DROP, RECREATE, CREATE OR ALTER, or EXECUTE BLOCK) and end with the last END statement of the body.

The header provides the module name and defines any input and output parameters or — for functions — the return type.Stored procedures and PSQL blocks may have input and output parameters.Functions may have input parameters and must have a scalar return type.Triggers do not have either input or output parameters, but DML triggers do have the NEW and OLD “records”, and INSERTING, UPDATING and DELETING variables.

The header of a trigger indicates the DML event (insert, update or delete, or a combination) or DDL or database event and the phase of operation (BEFORE or AFTER that event) that will cause it to “fire”.