User's Guide
PART 1. Working with Databases
CHAPTER 10. Using Procedures, Triggers, and Batches
Procedures and triggers store procedural SQL statements in a database for use by all applications.
Procedures and triggers can include control statements that allow repetition (LOOP statement) and conditional execution (IF statement and CASE statement) of SQL statements.
Procedures are invoked with a CALL statement, and use parameters to accept values and return values to the calling environment. Procedures can also return result sets to the caller. Procedures can call other procedures and fire triggers.
Triggers are associated with specific database tables. They are invoked automatically (fired) whenever rows of the associated table are inserted, updated or deleted. Triggers do not have parameters and cannot be invoked by a CALL statement. Triggers can call procedures and fire other triggers.
User-defined functions are one kind of stored procedure that returns a single value to the calling environment. User-defined functions do not modify parameters passed to them. They broaden the scope of functions available to queries and other SQL statements.