Oracle 外毗邻实现代码_周建明数据恢复硬盘专修中
日期:2014-06-07 / 人气: / 来源:网络
1. LEFT OUTER JOIN:左外关联
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
等价于
SELECT e.last_name, e.department_id, d.department_name
FROM employees e, departments d
WHERE e.department_id=d.department_id( );
结果为:所有员工及对应部门的记录,包括没有对应部门编号department_id的员工记录。
2. RIGHT OUTER JOIN:右外关联
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
RIGHT OUTER JOIN departments d
ON (e.department_id = d.department_id);
等价于
SELECT e.last_name, e.department_id, d.department_name
FROM employees e, departments d
WHERE e.department_id( )=d.department_id;
结果为:所有员工及对应部门的记录,包括没有任何员工的部门记录。
3. FULL OUTER JOIN:全外关联
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
FULL OUTER JOIN departments d
ON (e.department_id = d.department_id);
结果为:所有员工及对应部门的记录,包括没有对应部门编号department_id的员工记录和没有任何员工的部门记录。
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
LEFT OUTER JOIN departments d
ON (e.department_id = d.department_id);
等价于
SELECT e.last_name, e.department_id, d.department_name
FROM employees e, departments d
WHERE e.department_id=d.department_id( );
结果为:所有员工及对应部门的记录,包括没有对应部门编号department_id的员工记录。
2. RIGHT OUTER JOIN:右外关联
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
RIGHT OUTER JOIN departments d
ON (e.department_id = d.department_id);
等价于
SELECT e.last_name, e.department_id, d.department_name
FROM employees e, departments d
WHERE e.department_id( )=d.department_id;
结果为:所有员工及对应部门的记录,包括没有任何员工的部门记录。
3. FULL OUTER JOIN:全外关联
SELECT e.last_name, e.department_id, d.department_name
FROM employees e
FULL OUTER JOIN departments d
ON (e.department_id = d.department_id);
结果为:所有员工及对应部门的记录,包括没有对应部门编号department_id的员工记录和没有任何员工的部门记录。
Oracle时间日期操作方法小结第1/2页
Oracle时间日期操作方法小结,相信会对各位网友学习和提高Oracle水平有帮助。。
Oracle,时间日期
作者:管理员
推荐内容 Recommended
- 江苏飞浩信息科技期待您的加入07-20
- 江苏飞浩科技欢迎您07-19
相关内容 Related
- 江苏飞浩信息科技期待您的加入07-20
- 江苏飞浩科技欢迎您07-19