对于以下关系模式:
Teacher(tno , tname ,tage,tsex,title)
project(pno,pname, tno,classify)
work(tno,pno,pt)
其中teacher为教师关系,tno为教师编号,tname为教师名,tage为年龄tsex为性别,title为教师的职称;
project为项目关系,pno为项目号,pname为项目名,tno为负责人教师编号,classify 为项目分类;
work为参与关系,pt为某个教师在参与某个项目的工作量。
1. 创建职称为副教授的女教师的视图fn_vie
CREATE VIEW fn_vie
AS
SELECT tno,tname,tage
FROM teacher
WHERE title=’副教授’AND tsex=’女’;
2. 创建申请了省级项目的教师教师号,教师名建立视图sj_vie
CREATE VIEW sj_vie
AS
SELECT tno,tname
FROM teacher
WHERE tno IN(SELECT tno
FROM project
WHERE classify=’省级’);
3. 在fn_vie上查询职称为副教授的女教师参与的项目的项数
SELECT COUNT(DISTINCT pno)
FROM work
WHERE tno IN
(SELECT tno
FROM fn_vie);
4. 在sj_vie上查询参与省级项目的工作量的总和
SELECT SUM(pt)
FROM work
WHERE pno IN
(SELECT pno
FROM project
WHERE tno IN
(SELECT tno
FROM sj_vie));
5. 有以下建立视图的语句:
CREATE VIEW t_vie AS
SELECT tno
FROM work
WHERE pt>40
GROUP BY tno
HAVING COUNT(*)>3
请将此视图查询语句完成视图消解
SELECT tno FROM t_vie
等价于:
SELECT tno
FROM work
WHERE pt>40
GROUP BY tno
HAVING COUNT(*)>3;