Syntax:
[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]

The statement list within a WHILE statement is repeated as long as the
search_condition is true. statement_list consists of one or more
statements.

A WHILE statement can be labeled. See [HELP BEGIN END] for the rules
regarding label use.

URL: http://dev.mysql.com/doc/refman/5.1/en/while-statement.html

