7 deptno NUMBER(4) REFERENCES tb_dept(deptno) --外键约束 8 ); --建表时指定了约束名 SQL> CREATE TABLE tb_constraint_2 2 ( 3 empno NUMBER CONSTRAINT pk_tb_cons2_empno PRIMARY KEY, 4 ename VARCHAR2(20) CONSTRAINT nn_tb_cons2_empno NOT NULL, 5 email VARCHAR2(60) CONSTRAINT un_tb_...
create table t_emp(empno int, deptno int, ename varchar(20), esex char(2)); alter table t_emp add constraint PK_EMPNO primary key(empno); create table t_dept(deptno int, dname varchar(20)); alter table t_dept add constraint PK_DEPTNO primary key(deptno); /* deptno外键引用到了部门...
数据库原理课后题答案⏺CONSTRAINT PK_SC PRIMARY KEY (Deptno));CREATE TABLE EMP(Empno NUMBER(4) primary key,Ename VARCHAR(10),Age NUMBER(2),CONSTRAINT C1 CHECK (Aage < =60),Job VARCHAR(9),Sal NUMBER(7,2),Deptno NUMBER(2),CONSTRAINT FK_DEPTNOFOREIGN KEY(Deptno)REFERENCES DEPT(Deptno));...
7deptno NUMBER(4)REFERENCEStb_dept(deptno)--外键约束 8); --建表时指定了约束名 SQL>CREATETABLEtb_constraint_2 2( 3empno NUMBERCONSTRAINTpk_tb_cons2_empnoPRIMARYKEY, 4ename VARCHAR2(20)CONSTRAINTnn_tb_cons2_empnoNOTNULL, 5email VARCHAR2(60)CONSTRAINTun_tb_cons2_emailUNIQUE, 6salNUMBER(5...
7deptno NUMBER(4)REFERENCEStb_dept(deptno)--外键约束 8); --建表时指定了约束名 SQL>CREATETABLEtb_constraint_2 2( 3empno NUMBERCONSTRAINTpk_tb_cons2_empnoPRIMARYKEY, 4ename VARCHAR2(20)CONSTRAINTnn_tb_cons2_empnoNOTNULL, 5email VARCHAR2(60)CONSTRAINTun_tb_cons2_emailUNIQUE, ...
SQL> alter table emp add constraint emp_deptno_fk foreign key(deptno) references dept (deptno) on delete cascade; 第二种方式,删除父表中的对应行,会将对应子表中的所有匹配行的外键约束列置为NULL,通过 on delete set null 子句实施: SQL> alter table emp add constraint emp_deptno_fk foreign key...
7 deptno NUMBER(4) REFERENCES tb_dept(deptno) --外键约束 8 ); --建表时指定了约束名 SQL> CREATE TABLE tb_constraint_2 2 ( 3 empno NUMBER CONSTRAINT pk_tb_cons2_empno PRIMARY KEY, 4 ename VARCHAR2(20) CONSTRAINT nn_tb_cons2_empno NOT NULL, ...
deptno char(2) not null constraint emp_deptno_fk references dept, constraint emp_pk primary key(empno,ename) ) create table employees ( empno number(5), ename varchar2(15), phone varchar2(15), email varchar2(30) unique, deptno number(3) not null, ...
7deptno NUMBER(4)REFERENCEStb_dept(deptno)--外键约束 8); --建表时指定了约束名 SQL>CREATETABLEtb_constraint_2 2( 3empno NUMBERCONSTRAINTpk_tb_cons2_empnoPRIMARYKEY, 4ename VARCHAR2(20)CONSTRAINTnn_tb_cons2_empnoNOTNULL, 5email VARCHAR2(60)CONSTRAINTun_tb_cons2_emailUNIQUE, ...
deptno char(2) not null constraint emp_deptno_fk references dept, constraint emp_pk primary key(empno,ename) ) create table employees ( empno number(5), ename varchar2(15), phone varchar2(15), email varchar2(30) unique, deptno number(3) not null, constraint emp_pk primary key(empno,en...