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mysql-merge合并表
[sql]
注意:
1 每个子表的结构必须一致,主表和子表的结构需要一致,
2 每个子表的索引在merge表中都会存在,所以在merge表中不能根据该索引进行唯一性检索。
3 子表需要是MyISAM引擎
4 AUTO_INCREMENT 不会按照你所期望的方式工作。
建表语句
create table tablename(正常的字段)engine=merge insert_method=last
insert_method:
有两个值如下:
LAST 如果你执行insert 指令来操作merge表时,插入操作会把数据添加到最后一个子表中。
FIRST 同理,执行插入数据时会把数据添加到第一个子表中。
例子:
create table user1( id int(10) not null auto_increment, name varchar(50), sex int(1), primary key(id) )engine=myisam charset=utf8; create table user2( id int(10) not null auto_increment, name varchar(50), sex int(10) ,primary key(id) )engine=myisam charset=utf8; insert into user1 (name,sex) values('张三',0); insert into user2 (name,sex) values('lisi',1); mysql> select * from user1; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | 张三 | 0 | +----+------+------+ mysql> select * from user2; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | lisi | 1 | +----+------+------+ create table alluser( id int(10) not null auto_increment, name varchar(50), sex int(10), index(id) )type=merge union=(user1,user2) insert_method=last; mysql> select * from alluser; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | 张三 | 0 | | 1 | lisi | 1 | +----+------+------+ mysql> insert into alluser(name,sex) values('嘿嘿',0); mysql> select * from user1; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | 张三 | 0 | +----+------+------+ 1 row in set (0.00 sec) mysql> select * from user2; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | lisi | 1 | | 2 | 嘿嘿 | 0 | +----+------+------+
2 rows in set (0.00 sec)
//他把这条数据存入了user2表里是因为我们的insert_method的参数填写的是last
mysql> update alluser set sex=replace(sex,0,1) where id=2; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | 张三 | 0 | | 1 | lisi | 1 | | 2 | 嘿嘿 | 1 | +----+------+------+
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