1.多表查询

　　SELECT a.id,catid,thumb,title FROM v9_gamedown as a LEFT JOIN v9_gamedown_data as b ON a.id=b.id WHERE a.status=99 and b.artist="'.$artist.'" limit 0,'.$num

2.把一张表中的字段移动到另一张表

　　update v9_gamedown_data as a set a.n_language = (select language from v9_gamedown as b where b.id = a.id)
　　update v9_gamedown_data as a set a.n_thumb2 = (select thumb2 from v9_gamedown as b where b.id = a.id)

3.字符串替换

　　UPDATE `v9_record_data` SET `attach2` = REPLACE(`attach2`, 'http://www.fengzigame.com/uploadfile/2014/0326/', 'http://files.fengzigame.com/cd/share/') WHERE `id` > 0;

　　UPDATE `v9_record_data` SET `attach` = REPLACE(`attach`, 'http://www.fengzigame.com/uploadfile/', 'http://files.fengzigame.com/cd/pro/') WHERE `id` > 0;

4.把一张表的字段复制到另外一张表中

　　insert into apple_id (`apple_id`,`password`,`UDID`)  select `apple_id`,`password`,`UDID` from appleaccount where UDID is not NULL;

5.建表

CREATE TABLE IF NOT EXISTS `v9_guan_history` (

  `id` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,

  `tagid` int(10) DEFAULT '0' COMMENT 'tagid',

  `email` VARCHAR(32) NOT NULL DEFAULT '' COMMENT 'appleid',

  `idfa` VARCHAR(64) DEFAULT '' COMMENT '设备码',

  `status` tinyint(1) unsigned  DEFAULT 0 COMMENT '类型',

  `activedate` VARCHAR(12)  DEFAULT '' COMMENT '激活时间',

  `installdate` VARCHAR(12)  DEFAULT '' COMMENT '装机时间',

  PRIMARY KEY (`id`),

  KEY `mykey` (`tagid`,`installdate`)

) ENGINE=MyISAM DEFAULT CHARSET=utf8;

6.删除字段

　　ALTER TABLE `haha2` DROP `name`

7.添加字段

　　ALTER TABLE `v9_fx_history` ADD `devid` int(11) DEFAULT 0 AFTER `uid` ;

8.修改字段名称

　　ALTER TABLE `v9_dxt_history` CHANGE `madein` `area` varchar(16) DEFAULT ''

9.修改字段类型

　　ALTER TABLE `haha2` CHANGE `num` `num` INT( 11 ) NULL DEFAULT '0'

10.修改表名

　　ALTER TABLE `haha2` RENAME `haha` ;

11.修改字段的位置

　　ALTER TABLE tb_dept1 MODIFY column1 VARCHAR(12) AFTER location;

12.修改表的存储引擎

　　ALTER TABLE tb_dev ENGINE=MyISAM;

11.

　　复制旧表的数据到新表(假设两个表结构一样)

　　INSERT INTO 新表 SELECT * FROM 旧表

　　复制旧表的数据到新表(假设两个表结构不一样)

　　INSERT INTO 新表(字段1,字段2,…….) SELECT 字段1,字段2,…… FROM 旧表

12.多表更新

　　UPDATE v9_qd_dev dev, v9_qd_account user SET dev.storename = user.storename  WHERE dev.storeid = user.id ;

13.添加索引

　　ALTER TABLE book ADD INDEX mykey(id,name,num);

　　ALTER TABLE book ADD UNIQUE INDEX uniquekey (tagid);

14.查看表中的索引

　　SHOW INDEX FROM book \G;

15.删除索引

　　ALTER TABLE book DROP INDEX mykey;

　　DROP INDEX mykey ON book;

16.三张关联表的查询

select v9_app_enjoy.id,v9_app_enjoy.gid,title,tagid,attach4 from v9_app_enjoy left join v9_gamedown2 on v9_app_enjoy.gid = v9_gamedown2.id left join v9_gamedown2_data on v9_gamedown2_data.id=v9_gamedown2.id;

select title,tagid,attach4 from v9_app_enjoy as a left join v9_gamedown2 as b on a.gid = b.id left join v9_gamedown2_data as c on c.id=b.id  where a.uid in (5634,11211) ORDER BY a.id desc limit 2;

17. 多表分组更新

update v9_qd_account as u,(select sum(money) as money, storeid from v9_qd_mingxi where inputtime>0 group by storeid) as m set now_money= now_money+money where u.id = m.storeid

18.关联删除

delete from v9_gamedown2  where status = 0

delete v9_gamedown2_data from v9_gamedown2_data LEFT JOIN v9_gamedown2 ON v9_gamedown2_data.id=v9_gamedown2.id WHERE v9_gamedown2.id IS NULL

20.在一个字段前添加字符串

　　update aa set name=concat('x',name)

21.模糊查询 关联度匹配

select tagid,catid

from v9_gh_app

where iscan != 1 and ( title LIKE '%无敌%' OR title LIKE '%流浪%' OR title LIKE '%方舟%')

ORDER BY (CASE WHEN title LIKE '%无敌%' THEN 1000 ELSE 0 END) + (CASE WHEN title LIKE '%流浪%' THEN 990 ELSE 0 END) + (CASE WHEN title LIKE '%方舟%' THEN 980 ELSE 0 END) DESC