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 quotation marks and with each instance of backslash ("\"),
single quote ("'"), ASCII NUL, and Control+Z preceded by a backslash.
If the argument is NULL, the return value is the word "NULL" without
enclosing single quotation marks.

URL: http://dev.mysql.com/doc/refman/5.5/en/string-functions.html

