【2019-2020春学期】数据库作业13：SQL练习8 - CHECK / CONSTRAINT / TRIGGER / PROCEDURE/ FUNCTION

【例5.1】将Student表中的Sno属性定义为码。
CREATE TABLE Student
(Sno CHAR(9) PRIMARY KEY,
Sname CHAR(20) NOT NULL,
Ssex CHAR(2),
Sage SMALLINT,
Sdept CHAR(20)
);
也可以这样：

CREATE TABLE Student
(Sno CHAR(9),
Sname CHAR(20) NOT NULL,
Ssex CHAR(2),
Sage SMALLINT,
Sdept CHAR(20),
PRIMARY KEY(Sno)
);

【例5.2】将SC表中的Sno、Cno属性组定义为码。

CREATE TABLE SC
(Sno CHAR(9) NOT NULL,
Cno CHAR(4) NOT NULL,
Grade SMALLINT,
PRIMARY KEY(Sno,Cno)
);
在进行实体完整性检查和违约处理检查主码值是否唯一，如果不唯一则拒绝插入或修改；检查主码的各个属性是否为空，只要有一个为空就拒绝插入或修改。

【例5.3】定义SC中的参照完整性

CREATE TABLE SC
(Sno CHAR(9) NOT NULL,
Cno CHAR(4) NOT NULL,
Grade SMALLINT,
PRIMARY KEY(Sno,Cno),
FOREIGN KEY(Sno) REFERENCES Student(Sno),
FOREIGN KEY(Cno) REFERENCES Course(Cno)
);
无异常

【例5.4】显式说明参照完整性的违约处理示例

CREATE TABLE SC
(Sno CHAR(9) NOT NULL，
Cno CHAR(4) NOT NULL，
Grade SMALLINT,
PRIMARY KEY(Sno,Cno)，
FOREIGN KEY(Sno) REFERENCES Student(Sno)
ON DELETE CASCADE
ON UPDATE CASCADE,
FOREIGN KEY (Cno) REFERENCES Course(Cno)
ON DELETE NO ACTION
ON UPDATE CASCADE
);
可以根据应用要求定义属性上的约束条件在CREATE TABLE中定义属性。

【例5.5】在定义SC表时，说明Sno、Cno、Grade属性不允许为空值。

CREATE TABLE SC
(Sno CHAR(9) NOT NULL,
Cno CHAR(4) NOT NULL,
Grade SMALLINT NOT NULL,
PRIMARY KEY(Sno,Cno),
……
);
如此设置

【例5.6】建立部门表DEPT，要求部门名称Dname列值取值唯一，部门编号Deptno列为主码

CREATE TABLE DEPT
(Deptno NUMERIC(2),
Dname CHAR(9)UNIQUE NOT NULL,
Location CHAR(10),
PRIMARY KEY(Deptno)
);

【例5.7】Student表的Ssex只允许取“男”或“女”

CREATE TABLE Student
(Sno CHAR(9) PRIMARY KEY,
Sname CHAR(8)NOT NULL,
Ssex CHAR(2)CHECK(Ssex IN(‘男’,‘女’)),
Sage SMALLINT,
Sdept CHAR(20)
);
检验成功

【例5.7】Student表的Ssex只允许取“男”或“女”

CREATE TABLE Student
(Sno CHAR(9) PRIMARY KEY,
Sname CHAR(8)NOT NULL,
Ssex CHAR(2)CHECK(Ssex IN(‘男’,‘女’)),
Sage SMALLINT,
Sdept CHAR(20)
);

【例5.9】当学生的性别是男时，其名字不能以Ms.打头。

CREATE TABLE Student
(Sno CHAR(9),
Sname CHAR(8) NOT NULL,
Ssex CHAR(2),
Sage SMALLINT,
Sdept CHAR(20),
PRIMARY KEY(Sno),
CHECK(Ssex=‘女’ OR Sname NOT LIKE ‘Ms.%’)
);
插入元组或修改属性的值，要知道关系数据库管理系统检查元组上的约束条件是否被满足，如果不满足则操作被拒绝执行 。

【例5.10】建立学生登记表Student，要求学号在90000-99999之间，姓名不能取空值，年龄小于30，性别只能是“男”或“女”。

CREATE TABLE Student
(Sno NUMERIC(6)
CONSTRAINT C1 CHECK(Sno BETWEEN 90000 AND 99999),
Sname CHAR(20)
CONSTRAINT C2 NOT NULL,
Sage NUMERIC(3)
CONSTRAINT C3 CHECK(Sage<30),
Ssex CHAR(2)
CONSTRAINT C4 CHECK(Ssex IN(‘男’,‘女’)),
CONSTRAINT StudentKey PRIMARY KEY(Sno)
);
无异常

【例5.11】建立教师表TEACHER，要求每个教师的应发工资不低于3000元。应发工资列Sal与扣除项Deduct之和

CREATE TABLE TEACHER
(Eno NUMERIC(4) PRIMARY KEY,
Ename CHAR(10),
Job CHAR(8),
Sal NUMERIC(7,2),
Deduct NUMERIC(7,2),
Deptno NUMERIC(2),
CONSTRAINT TEACHERKey FOREIGN KEY(Deptno)
REFERENCES DEPT(Deptno),
CONSTRAINT C1 CHECK(Sal+Deduct>=3000)
);
基本符合

【例5.12】去掉例5.10Student表中对性别的限制

ALTER TABLE Student DROP CONSTRAINT C4;
这个比较简单

【例5.13】修改表Student中的约束条件，要求学号在900000-999999之间，年龄由小于30改为小于40。

ALTER TABLE Student
DROP CONSTRAINT C1;
ALTER TABLE Student
ADD CONSTRAINT C1 CHECK(Sno BETWEEN 900000 AND 999999);
ALTER TABLE Student
DROP CONSTRAINT C3;
ALTER TABLE Student
ADD CONSTRAINT C3 CHECK(Sage<40);
重复几遍大致一样的操作。

【例5.21】当对表SC的Grade属性进行修改时，若分数增加了10%，则将此次操作记录到另一个表SC_U(Sno,Cno,Oldgrade,Newgrade)中，其中Oldgrade是修改前的分数，Newgrade是修改后的分数。

首先我们创建SC_U：

CREATE TABLE SC_U
(Sno CHAR(9) PRIMARY KEY,
Cno CHAR(9),
OldGrade SMALLINT,
NewGrade SMALLINT
);

然后我们创建触发器：

CREATE TRIGGER SC_T
AFTER UPDATE OF Grade ON SC
REFERENCING
OLDROW AS OldTuple,
NEWROW AS NewTuple
FOR EACH ROW
WHEN(NewTuple.Grade>=1.1*OldTuple.Grade)
INSERT INTO SC_U(Sno,Cno,OldGrade,NewGrade)
VALUES(OldTuple.Sno,OldTuple.Cno,OldTuple.Grade,NewTuple.Grade)

T-SQL的写法：

CREATE TRIGGER SC_T
ON SC
FOR UPDATE
AS
declare @OLD SMALLINT
declare @NEW SMALLINT
declare @SNO CHAR(9)
declare @CNO CHAR(4)
IF(UPDATE(Grade))
BEGIN
select @OLD =Grade FROM DELETED
select @NEW =Grade FROM INSERTED
select @SNO =Sno FROM SC
select @CNO =Cno FROM SC
IF(@NEW>=1.1*@OLD)
INSERT INTO SC_U(Sno,Cno,Oldgrade,Newgrade)
VALUES (@SNO,@CNO,@OLD,@NEW)
END

【例5.22】将每次对表Student的插入操作所增加的学生个数记录到表StudentInsertLog中。

CREATE TRIGGER Student_Count
AFTER INSERT ON Student
REFERENCING
NEW TABLE AS DELTA
FOR EACH STATEMENT
INSERT INTO StudentInsertLog (Numbers)
SELECT COUNT(*) FROM DELTA

T-SQL写法：

CREATE TRIGGER Student_Time
ON Student
AFTER
AS
INSERT
INTO Student
INSERT INTO StudentInsertLog(Numbers)
SELECT COUNT(*) FROM Student;

【例5.23】定义一个BEFORE行级触发器，为教师表Teacher定义完整性规则，教授的工资不低于4000元，如果低于4000元，自动改为4000元

CREATE TRIGGER Insert_Or_Update_Sal
BEFORE INSERT OR UPDATE ON Teacher
FOR EACH ROW
BEGIN
IF(new.Job=‘教授’) AND (new.Sal<4000)
THEN new.Sal :=4000;
END IF;
END;

T-SQL写法:

CREATE TRIGGER Insert_Or_Update_Sal
ON Teacher
FOR UPDATE,INSERT
AS
IF UPDATE(Sal)
BEGIN
declare @TNO CHAR(9)
declare @TNAME CHAR(9)
declare @JOB CHAR(9)
declare @SAL SMALLINT

select @SAL = Sal FROM INSERTED
select @TNO =Tno FROM Teacher
select @TNAME =Tname FROM Teacher
select @JOB =Job FROM Teacher

IF(@SAL<4000 AND @JOB='教授')
UPDATE Teacher
SET SAL=4000
WHERE Sal<4000 AND Job='教授'

END

【例8.8】利用存储过程来实现下面的应用：从账户1转指定数额的款项到账户2中。

CREATE OR REPLACE PROCEDURE TRANSFER(inAccount INT,outAccount INT,amount FLOAT)
AS DECLARE
totalDepositOut Float;
totalDepositIn Float;
inAccountnum INT;
BEGIN
SELECT Total INTO totalDepositOut FROM Accout
WHERE accountnum=outAccount;
IF totalDepositOut IS NULL THEN
ROLLBACK;
RETURN
END IF;
IF totalDepositOut< amount THEN
ROLLBACK;
RETURN
END IF
SELECT Accountnum INTO inAccountnum FROM Account
WHERE accountnum=inAccount;
IF inAccount IS NULL THEN
ROLLBACK;
RETURN;
END IF;
UPDATE Account SET total=total-amount WHERE accountnum=outAccount;
UPDATE Account SET total=total + amount
WHERE accountnum=inAccount;
COMMIT;
END;
无异常

【例8.9】从账户01003815868转10000元到01003813828账户中。

CALL PROCEDURE TRANSFER(01003813828,01003815868,10000`);
这个就比较简单了