3.数据库设计步骤 CREATE TABLE Table2( COL 2 VARCHAR (10) NOT NULL, COL 3 VARCHAR(20)NOT NULL, COL 4 VARCHAR (10) NOT NULL UNIQUE COL O VARCHAR(20)NOT NULL, CONSTRAINT PK Table21 PRIMARY KEY NONCLUSTERED(COL 2) Go CREATE TABLE Tablel COL O VARCHAR (20) NOT NULL COL 1 NUMERIC(5) NOT NULL CONSTRAINT PK Table10 PRIMARY KEY NONCLUSTERED(COL 0) Go ALTER TABLE Table2 ADD CONSTRAINT FK Table20 FOREIGN KEY(COL 0) REFERENCES Tablel(COL 0) GO
3. 数据库设计步骤 CREATE TABLE Table2 ( COL_2 VARCHAR ( 10 ) NOT NULL, COL_3 VARCHAR ( 20 ) NOT NULL, COL_4 VARCHAR ( 10 ) NOT NULL UNIQUE, COL_0 VARCHAR ( 20 ) NOT NULL, CONSTRAINT PK_Table21 PRIMARY KEY NONCLUSTERED (COL_2) ) GO CREATE TABLE Table1 ( COL_0 VARCHAR ( 20 ) NOT NULL, COL_1 NUMERIC ( 5 ) NOT NULL, CONSTRAINT PK_Table10 PRIMARY KEY NONCLUSTERED (COL_0) ) GO ALTER TABLE Table2 ADD CONSTRAINT FK_Table20 FOREIGN KEY (COL_0) REFERENCES Table1 (COL_0) GO
3.数据库设计步骤 <<Non-Identifying>> Table2 Tablel 0..1 PK COL 2: VARCHAR (10) PK COL 0: VARCHAR (20) COL 3: VARCHAR (20) COL 1: NUMERIC(5. 0 CCL 4: DOM O 0.* FK COL 0: VARCHAR(20) ◆<K>> PK Table100 ◆<P> PK Table210 ◆<F> FK Table200 外键可以为空
3. 数据库设计步骤 外键可以为空