Find the % character in a LIKE query

I've an SQL database and I would like to do a query who show all the datas containing the sign "%". Normally, to find a character (for example: "z") in a database I use a query like this :

mysql_query("SELECT * FROM mytable WHERE tag LIKE '%z%'");

But here, I want to found the % character, but in SQL it's a joker so when I write:

mysql_query("SELECT * FROM mytable WHERE tag LIKE '%%%'");
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It show me all my datas. So how to found the % character in my SQL datas ?

Thanks

You can escape the % sign with a backslash:

SELECT * FROM mytable WHERE tag LIKE '%\%%'

Quoting from MySQL 5.0 Reference Manual :: 8.1.1 Strings:

The \% and \_ sequences are used to search for literal instances of % and _ in pattern-matching contexts where they would otherwise be interpreted as wildcard characters.

Here is a standard way:

SELECT * FROM mytable WHERE tag like '%|%%' ESCAPE '|'