t optimizer_goal = rule;
truncate table plan_table;
REM -- find direct reports to KING
explain plan set statement_id = 'IN' for
select ename from emp e
where mgr in (select empno from emp where ename = 'KING');
explain plan set statement_id = 'JOIN-IN' for
select e1.ename from emp e1,(select empno from emp where ename = 'KING') e2
where e1.mgr = e2.empno;
explain plan set statement_id = 'EXISTS' for
select ename from emp e
where exists (select 0 from emp where e.mgr = empno and ename = 'KING');
explain pl页码：[1] [2] [3] [4] [5] [6] [7] [8] 第6页、共8页 |
