ORACLE约束:主键，外键，非空，唯一，条件

ORACLE约束:主键，外键，非空，唯一，条件

create table COMPUTERS(    CNO NUMBER(3) CONSTRAINT PK_COMPUTERS PRIMARY KEY,    CUSER VARCHAR(4)    );INSERT INTO COMPUTERS(CNO,CUSER) VALUES(1,'MIKE');create table CPU(    CPUNO NUMBER(3) CONSTRAINT PK_CPU PRIMARY KEY,    COMPUTERNO NUMBER(3),CONSTRAINT FK_CPU FOREIGN KEY(COMPUTERNO) REFERENCES COMPUTERS(CNO),    BUYTIME DATE NOT NULL,    CPUMODEL VARCHAR2(64) UNIQUE,    PRICE NUMBER(7,2) CONSTRAINT CPU_PRICE CHECK(PRICE>0 AND PRICE < 3000)    );INSERT INTO CPU(CPUNO,COMPUTERNO,BUYTIME,CPUMODEL,PRICE) VALUES(888,1,SYSDATE,'MVBCQ-B3VPW-CT369-VM9TB-YFGBP',555.55);