MySQL 5.7 Release Notes
[begin_label:] BEGIN
[statement_list]
END [end_label]
BEGIN ... END
syntax is used for writing compound statements, which can appear
within stored programs (stored procedures and functions, triggers,
and events). A compound statement can contain multiple statements,
enclosed by the BEGIN and
END keywords.
statement_list represents a list of one
or more statements, each terminated by a semicolon
(;) statement delimiter. The
statement_list itself is optional, so
the empty compound statement (BEGIN END) is
legal.
BEGIN ... END
blocks can be nested.
Use of multiple statements requires that a client is able to send
statement strings containing the ; statement
delimiter. In the mysql command-line client,
this is handled with the delimiter command.
Changing the ; end-of-statement delimiter (for
example, to //) permit ; to
be used in a program body. For an example, see
Section 23.1, “Defining Stored Programs”.
A BEGIN ...
END block can be labeled. See
Section 13.6.2, “Statement Labels”.
The optional [NOT] ATOMIC clause is not
supported. This means that no transactional savepoint is set at
the start of the instruction block and the
BEGIN clause used in this context has no effect
on the current transaction.
Note
Within all stored programs, the parser treats
BEGIN [WORK]
as the beginning of a
BEGIN ...
END block. To begin a transaction in this context, use
START
TRANSACTION instead.