If you use MySQL 5.1, you can you use the information_schema database, which contains among others the list of all tables in your database ...
then you can for example be used to generate your request.
SELECT CONCAT ('UPDATE test.', TABLE_NAME, 'SET field1 = REPLACE (field1, "string1", "string1 ");') INFORMATION_SCHEMA.TABLES FROM WHERE TABLE_SCHEMA =' test ';
- > This query will give you a result that you can just paste in the client: