SQL语句培训文档.ppt

1、2008年10月,中国电力科学院配电与农电研究院,ORACLE数据库,SQL语句培训,（一）四类SQL语句,1、数据表创建语句,创建员工数据表:,CREATE TABLE Employee (Em_id number(8), Em_name varchar(20), dp_id number(8)， salary number(6);,插入演示数据:,INSERT INTO Employee VALUES(1,陈红卫,1,4000); INSERT INTO Employee VALUES(2,骆誉明,1,2800); INSERT INTO Employee VALUES(3,汪金海,2,5

2、000); INSERT INTO Employee VALUES(4,王敏,2,3500); INSERT INTO Employee VALUES(5,杜康乐,2,1800); INSERT INTO Employee VALUES(6,赵方,8,8000); Commit;,1、数据表创建语句,创建部门数据表:,CREATE TABLE Department (dp_id number(8), dp_name varchar(20), Up_DepID number );,插入演示数据:,INSERT INTO Department VALUES(1,技术组,0); INSERT INT

3、O Department VALUES(2,服务组,0); INSERT INTO Department VALUES(3,工程组,0); INSERT INTO Department VALUES(6, 财务部,2); COMMIT;,说明：部门编号、部门名称、上级部门编号。,1、内关联 Inner Join,查询语句:,SELECT * FROM Employee EMP INNER JOIN Department DP ON EMP.dp_id=DP.DP_ID,1、左关联 Left Join,查询语句:,SELECT * FROM Employee EMP Left JOIN Depa

4、rtment DP ON EMP.dp_id=DP.DP_ID,说明：左关联查询，只对（Left）后面的数据表进行过滤。,查询结果：,1、右关联和全关联,Right Join:,SELECT * FROM Employee EMP Right JOIN Department DP ON EMP.dp_id=DP.DP_ID,说明：右关联查询，只对（Right）后面的数据表进行过滤。,Full Join:,提问：此时查询的结果如何？请写出查询结果。,SELECT * FROM Employee EMP Full JOIN Department DP ON EMP.dp_id=DP.DP_ID,说

5、明：Full查询，不再对两边的数据表进行过滤。,提问：此时查询的结果如何？请写出查询结果。,1、自然连接和Using语句,Natural Join:,SELECT * FROM Employee EMP NATURAL JOIN Department DP,说明：只有两个数据表中有相同的列，并且使用该列进行关联时，才可以使 用自然连接。 自然连接查询结果和内连接查询相同。,Using子句:,SELECT * FROM Employee ST INNER JOIN DEPMENT DP USING (dp_id),说明：两个数据表中有相同的列时，可以使用该查询语句。,1、子查询语句,In 语句:

6、,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。,1、第一章试题,1、阐述四种关联查询的区别； 2、自己独立编写，查询上级部门编号为0部门的员工，（普通关联查询、IN语