here is the test. create table t1(id int, name char(10)); create table t2(id int, name char(12)); insert into t1 values(100, 'yang'); insert into t2 values(200, 'yang'); commit; -- return 1 row select * from t1, t2 where t1.name = t2.name and t1.name = 'yang'; -- return 1 row se