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Select Concat( 'update ', table_schema, '.', table_name,
               ' set ', column_name,
               '=replace(', column_name, ',''old_text'',''new_text'');'
             )
From information_schema.columns
Where (data_type Like '%char%' or data_type like '%text' or data_type like '%binary')
  And table_schema = 'dbname';