Oracle之多表查询

多表查询的基础语法

SELECT {DISTINCT} * |查询列 1 别名1,查询列 2 别名2,…

FROM 表名称1 别名1 , 名称2 别名2 ,…

{WHERE 条件(s)}

{ORDER BY 排序字段ASC|DESC , 同时查询ACS | DESC ,…}

给出几个例子吧。

1.

SELECT e.ename,e.sal,d.dname,s.grade,m.ename,m.sal,ms.grade
FROM emp e,dept d,salgrade s,emp m,salgrade ms
WHERE e.deptno=d.deptno AND
e.sal BETWEEN s.losal AND s.hisal AND e.mgr=m.empno
AND m.sal BETWEEN ms.losal AND ms.hisal;

2.

SELECT e.ename,e.sal,d.dname,
DECODE(s.grade,1,'第五等工资',2,'第四等工资',3,'第三等工资'
,4,'第二等工资',5,'第一等工资'),m.ename,m.sal,
DECODE(ms.grade,1,'第五等工资',2,'第四等工资',3,'第三等工资'
,4,'第二等工资',5,'第一等工资')
FROM emp e,dept d,salgrade s,emp m,salgrade ms
WHERE e.deptno=d.deptno AND
e.sal BETWEEN s.losal AND s.hisal AND e.mgr=m.empno
AND m.sal BETWEEN ms.losal AND ms.hisal;


左、右连接

SQL:1999

SELECT table1.column,table2.column
FROM table1 [CROSS JOIN table2]|
[NATURAL JOIN table2]|
[JOIN table2 USING(column_name)]|
[JOIN table2 ON(table1.column_name=table2.column_name)]|
[LEFT|RIGHT|FULL OUTER JOIN table2 ON(table1.column_name=table2.column_name)];

这尼玛不怎么懂得说。。