【文件属性】:
文件名称:子查询语句-SQL语句培训文档
文件大小:539KB
文件格式:PPT
更新时间:2021-04-25 22:09:46
SQL语句 培训
1、子查询语句
In 语句:
SELECT * FROM Employee
WHERE dp_id IN (SELECT DP_ID FROM Department
WHERE UP_DEPID=0)
说明:查询部门编号为0(工程技术部)下级部门的人员。
EXISTS语句:
SELECT * FROM Employee A WHERE EXISTS
(SELECT DP_ID FROM Department B
WHERE UP_DEPID=0 AND A.dp_id=B.dp_id);
说明:和In语句查询出的结果一样,该语句查询的效率大大优于In语句。
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