MySQL query to search string in Master-Child tables and return all rows with Master-Child relation
SELECT  t1.*, 
        t2.*

FROM    Table1 AS t1
    LEFT JOIN
        Table2 AS t2
            ON WHERE t2s.FK_id = t1.PK_id

WHERE   t1.Table1_Title = 'search text'
   OR   EXISTS
        ( SELECT  *
          FROM    Table2 AS t2s
          WHERE   t2s.FK_id = t1.PK_id
            AND   t2s.Table2_Title = 'search text'
        ) ;