SQL 语句汇总-With子句

1.使用With 子句重用子查询
用于在sql多次使用相同的子查询时：
示例一、显示部门工资总和高于雇员工资总和三分之一的部门名及工资总和（两次相同子句）
  SQL> select dname,sum(sal) as dept_total  from emp,dept
             where emp.deptno=dept.deptno  group by dname
             having sum(sal)>
             (select sum(sal) *1/3 from emp,dept
             where emp.empno=dept.empno);

示例二、显示部门工资总和高于雇员工资总和三分之一的部门名及工资总和（使用with子句重用子查询）

        SQL> with summary as 
              (select dname,sum(sal) as dept_total  from emp,dept
                where emp.deptno=dept.deptno  group by dname
               )
               select dname,dept_total from summary dept_total>
               (select sum(dept_total)*1/3 from summary);