MySQL 8.0 Release Notes
MySQL 8.0 Source Code Documentation
This section describes the syntax for the
BEGIN ... END
compound statement and other statements that can be used in the body
of stored programs: Stored procedures and functions, triggers, and
events. These objects are defined in terms of SQL code that is
stored on the server for later invocation (see
Chapter 27, Stored Objects).
A compound statement is a block that can contain other blocks; declarations for variables, condition handlers, and cursors; and flow control constructs such as loops and conditional tests.