Syntax:
[begin_label:] LOOP
    statement_list
END LOOP [end_label]

LOOP implements a simple loop construct, enabling repeated execution of
the statement list, which consists of one or more statements, each
terminated by a semicolon (;) statement delimiter. The statements
within the loop are repeated until the loop is terminated. Usually,
this is accomplished with a LEAVE statement. Within a stored function,
RETURN can also be used, which exits the function entirely.

Neglecting to include a loop-termination statement results in an
infinite loop.

A LOOP statement can be labeled. For the rules regarding label use, see
[HELP labels].

URL: https://dev.mysql.com/doc/refman/8.0/en/loop.html

