mySQL query to search all tables within a database for a string?

Alternatively, if your database is not that huge, you can make a dump and make your search in the .sql generated file.

If you are using MySQL Workbench, you can do this by doing right click on the DB Schema you want to search into, and then "Search Table Data...".

In there you can select the "Search using REXEXP" option, and then type your text of search as usual. It will provide the DB rows matching your specific text.

You will need to check the "Search columns of all types" box as well.