SELECT 1 FROM dual FOR UPDATE;
SET autocommit=0;
SELECT 1 FROM dual FOR UPDATE;
SELECT 1 FROM dual FOR UPDATE OF tbl1  ;
SELECT 1 FROM dual a JOIN dual b;
SELECT 1, 3, 5, 6 , 'aa' FROM dual a JOIN dual b;
ROLLBACK;
SELECT 1 FROM dual FOR SHARE;
ROLLBACK;
SELECT 1 FROM dual LOCK IN SHARE MODE  ;
ROLLBACK;
SET autocommit=1;
SELECT 1 FROM dual FOR SHARE;
SELECT 1 FROM dual FOR UPDATE;