create TABLE zhao(
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id number primary key,
mingcheng nvarchar2(50),
neirong nvarchar2(50),
jiezhiriqi date,
zhuangtai nvarchar2(50)
);
create TABLE tou(
id number primary key,
zhao_id number,
toubiaoqiye nvarchar2(50),
biaoshuneirong nvarchar2(50),
toubiaoriqi date,
baojia number,
zhuangtai nvarchar2(50),
foreign KEY(zhao_id) REFERENCES zhao(id)
);
foreign key (zhao_id) references to zhao(id)
多了个to
--使用表级约束
CREATE TABLE table_name
(column_1 datatype ,
column_2 datatype ,
...
CONSTRAINT fk_column
FOREIGN KEY (column_1, column_i, ... column_n)
REFERENCES parent_table (column_1, column_i, ... column_n)
);
--使用列级约束
CREATE TABLE table_name
(column_1 datatype ,
column_2 datatype CONSTRAINT fk_column REFERENCES parent_table (column_name),
...
);
create TABLE zhao(\x0d\x0a id number primary key,\x0d\x0a mingcheng nvarchar2(50),\x0d\x0a neirong nvarchar2(50),\x0d\x0a jiezhiriqi date,\x0d\x0a zhuangtai nvarchar2(50)\x0d\x0a);\x0d\x0acreate TABLE tou(\x0d\x0a id number primary key,\x0d\x0a zhao_id number,\x0d\x0a toubiaoqiye nvarchar2(50),\x0d\x0a biaoshuneirong nvarchar2(50),\x0d\x0a toubiaoriqi date,\x0d\x0a baojia number,\x0d\x0a zhuangtai nvarchar2(50),\x0d\x0a foreign KEY(zhao_id) REFERENCES zhao(id)\x0d\x0a);\x0d\x0aforeign key (zhao_id) references to zhao(id)\x0d\x0a多了个to
主外键需要依托多表来创建，方法如下：
创建主表：
CREATE TABLE SCOTT.DEPT
(DEPTNO NUMBER(2,0) PARIMARY KEY,
DNAME VARCHAR2(14),
LOC VARCHAR2(13));
创建副表及外键：
CREATE TABLE EMP
(EMPNO NUMBER(4,0) PRIMARY KEY,
ENAME VARCHAR2(10),
JOB VARCHAR2(9),
MGR NUMBER(4,0),
HIREDATE DATE,
SAL NUMBER(7,2),
COMM NUMBER(7,2),
DEPTNO NUMBER(2,0),
CONSTRAINT FK_DEPTNO FOREIGN KEY (DEPTNO) REFERENCES DEPT (DEPTNO));
