Syntax:
QUOTE(str)

Quotes a string to produce a result that can be used as a properly
escaped data value in an SQL statement. The string is returned enclosed
by single quotes and with each instance of single quote ("'"),
backslash ("\"), ASCII NUL, and Control-Z preceded by a backslash. If
the argument is NULL, the return value is the word "NULL" without
enclosing single quotes.

URL: http://dev.mysql.com/doc/refman/5.1/en/string-functions.html

