MYSQL

优化之索引：

alter table go_member_go_record add INDEX `sindex`(`present`,`is_jiqi`,`shop_status`);

 

首先不同的表是无法使用索引的，联合索引指的是同一张表的不同字段。优化需要看两张表数据量。一般的做法是：select * from （select * from A where X = 'xxxx') as aa left join B on B.id=aa.id order by B.datetime;建立 单独对A.X A.id B.id 建立索引。

追问

你确定是用的是mysql吗？
你确定mysql按照如下的写法可以查到数据吗？
select * from （select * from A)

追答

当然是MySQL，    select * from （select * from A) as aa  要加别名的。这个叫嵌套查询，里面的句子叫子查询，目的是缩小范围。

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人人得宝，出现mobile重复出现，解决方法：
//添加普通索引
create index mobile on go_member(mobile);
//将所有mobile重复记录导入第三表 go_all
create table go_all select * from go_member where 1=2 
insert into go_all select * from go_member where mobile in (select mobile from go_member group by mobile having count(*)>1);
//将mobile重复记录中uid最小记录导入第三表 go_min
create table go_min select * from go_member where 1=2 
insert into go_min select * from go_member where mobile!='' or mobile is not null group by mobile having count(*)>1;
//删除mobile重复且uid非最小记录
delete from go_member where uid in(select uid from go_all) and uid not in(select uid from go_min);
//添加mobile唯一索引
alter table go_member add unique(mobile);
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解决方法：

delete  from menu_item  where parent_id =(select menu_item_id from menu_item where menu_data like '%manageVendors%');
delete  from menu_item  where parent_id =(select temp.menu_item_id from (select m.menu_item_id,m.menu_data from menu_item m) temp where temp.menu_data like '%manageVendors%');
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