?? table's rel.txt
字號:
User :
id number;
name varchar(20);
Address :
addr_name varchar(40);
第一種情況: 一對一關系
方法一:
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL ,
addr_name VARCHAR(40) CONSTRAINT addr_name_nl NOT NULL);
方法二:
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL );
CREATE TABLE address
( addr_name VARCHAR(40) CONSTRAINT addr_name_nl NOT NULL,
id NUMBER(2) CONSTRAINT user_id_fk REFERENCE user(id),
CONSTRAINT user_id_uq UNIQUE(addr_name,id));
第二種情況:一對多關系
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id_pk PRIMARY KEY ,
name VARCHAR(20) CONSTRAINT user_name_nl NOT NULL );
CREATE TABLE address
( addr_id NUMBER(2) CONSTRAINT addr_id_pk PRIMARY KEY ,
addr_name VARCHAR(20) CONSTRAINT addr_name_nl NOT NULL,
id NUMBER(2) CONSTRAINT addr_id_fk FOREIGN KEY(id) REFERENCE user(id));
第三種情況:多對多關系
CREATE TABLE user
( id NUMBER(2) CONSTRAINT user_id PRIMARY KEY ,
name VARCHAR(20) CONSTRAINT user_name NOT NULL );
CREATE TABLE address
( addr_id NUMBER(2) CONSTRAINT addr_id_pk PRIMARY KEY,
addr_name VARCHAR(40)CONSTRAINT addr_name_nl NOT NULL);
CREATE TABLE user_addr
( id NUMBER(2),
addr_id NUMBER(2),
CONSTRAINT user_addr_id_pk PRIMARY KEY(id,addr_id));
?? 快捷鍵說明
復制代碼
Ctrl + C
搜索代碼
Ctrl + F
全屏模式
F11
切換主題
Ctrl + Shift + D
顯示快捷鍵
?
增大字號
Ctrl + =
減小字號
Ctrl + -