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mysql alter table创建外键(Foreign Key) 的语句

ALTER TABLE Order ADD FOREIGN KEY ( userid ) REFERENCES app_user( id )
ON UPDATE RESTRICT

一个表有多个外键的情况：
ALTER TABLE `tablename`
ADD CONSTRAINT `FK_BOOK` FOREIGN KEY (`BOOKID`) REFERENCES `book` (`BOOKID`) ON DELETE CASCADE ON UPDATE CASCADE,
ADD CONSTRAINT `FK_USER` FOREIGN KEY (`USERID`) REFERENCES `user` (`USERID`) ON UPDATE CASCADE;

ALTER TABLE `dbname`.`tblname` ADD CONSTRAINT `FK_NAME` FOREIGN KEY `FK_NAME` (`USERID`)
  REFERENCES `USER` (`USERID`)
  ON DELETE CASCADE
  ON UPDATE CASCADE;

http://www.sofee.cn/blog/2006/08/07/28/

http://hi.baidu.com/jlhh/blog/item/69f9a011accf3c7eca80c48c.html

mysql> show variables;



D:\Dev_tools\mysql-5.0.24a-win32>cd bin

D:\Dev_tools\mysql-5.0.24a-win32\bin>mysqldump zzesweb > D:/zz.sql

D:\Dev_tools\mysql-5.0.24a-win32\bin>

http://www.stephanwiesner.de/

http://www.blogjava.net/max/rss

CREATE TABLE example(
id INT NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id),
name VARCHAR(30),
age INT)
<--------------------------->   Insert

INSERT INTO example
(name, age) VALUES('Timmy Mellowman', '23' )

<----------------------------->   update

UPDATE example SET age='22' WHERE age='21'

<------------------------------>  select

SELECT * FROM example  ;

SELECT * FROM example
WHERE name='Sandy Smith' ;

<---------------------------------->  delete

DELETE FROM example WHERE age='15'