摘要： 联合查询：1.等值连接:（内连接，自然连接）SQL> select d.deptno, d.dname, e.empno, e.ename, e.sal 2 from dept d, emp e 3 where d.deptno=e.deptno;13 rows selected.2.非等值连接:SQL> select e.ename, e.sal, s.grade 2 from emp e, salgrade s 3* where e.sal between s.losal and s.hisal3.自连接:SQL> select e.ename, m.ename 2 fr 阅读全文