CREATE TABLE STUDENT

(SNOCHAR(10) ,

SNAME CHAR(25),

SSEX CHAR(5),

SAGE NUMBER(2),              --CONSTRAINT,為約束對象取個別名

SDEPT CHAR(25),

CONSTRAINT PK_SNO PRIMARY KEY(SNO),

CONSTRAINT UK_SNAME UNIQUE(SNAME)

);

CREATE TABLE COURSE

(CNOCHAR(5),

CNAME CHAR(50) NOT NULL,

CPNOCHAR(5),                   --非空約束(NK)出錯時會出現完整的出錯提示，所以不需要用CONSTRAINT來取別名

CCREDIT INT,

CONSTRAINT PK_CNO PRIMARY KEY(CNO)

);

CREATE TABLE SC

(SNOCHAR(10),

CNOCHAR(5),

GRADE INT,

CONSTRAINT PK_SNO_CNO PRIMARY KEY(SNO,CNO),        --主碼有兩個屬性構成

CONSTRAINT FK_SNO FOREIGN KEY(SNO) REFERENCES STUDENT(SNO),

CONSTRAINT FK_CNO FOREIGN KEY(CNO) REFERENCES COURSE(CNO)

);

CREATE TABLE MEMBER

(MID NUMBER,

NAMEVARCHAR2(200) NOT NULL,

EMAIL VARCHAR2(50),

AGENUMBER,

SEXVARCHAR2(10)，

CONSTRAINT PK_MID_NAME PRIMARY KEY(MID,NAME),

CONSTRAINT UK_EMAIL UNIQUE(EMAIL),

CONSTRAINT CK_SEX CHECK(SEX IN('男','女')),        --檢查約束

CONSTRAINT CK_AGE CHECK(AGE BETWEEN 0 AND 200)

);

SELECT *

FROM user_constraints                                          --通過數據字典查看約束

WHERE TABLE_NAME='MEMBER';

ALTER TABLE MEMBER

ADD CONSTRAINT PK_MID        --增加主鍵約束

PRIMARY KEY(MID);

ALTER TABLE MEMBER

ADD CONSTRAINT CK_AGE        --增加檢查約束

CHECK(AGE BETWEEN 0 AND 200);

ALTER TABLE MEMBER

MODIFY(NAME VARCHAR2(20) NOT NULL);        --只能通過此方法增加非空約束

ALTER TABLE MEMBER

DISABLE CONSTRAINT UK_EMAIL;      --禁用UK_EMAIL約束

ALTER TABLE STUDENT

DISABLE CONSTRAINT PK_SNO CASCADE;  --字表中有約束，必須使用CASCADE才能成功

ALTER TABLE MEMBER

ENABLE CONSTRAINT UK_EMAIL;   --啟用約束,若想啟用，必須刪掉表中違反約束的數據

ALTER TABLE STUDENT

ENABLE CONSTRAINT PK_SNO;     --啟用約束

ALTER TABLE MEMBER

DROP CONSTRAINT UK_EMAIL;         --刪除約束，若要刪除主鍵約束，必須要級聯