set @s=concat('alter table ',concat(dbname, '.', dablename),' rename to ',concat(dbname, '.', tabletime
))
MySQL Proxy 支持事务,读写分离就会把这个作为切分转发依据之一;也支持跨库,但是不晓得你是否问的事务跨库?这个就不清楚了、谁知道请补充。
参考:
http://dev.mysql.com/doc/refman/5.6/en/mysql-proxy-using.html
http://dev.mysql.com/doc/refman/5.6/en/mysql-proxy-faq.html
1、where型子查询(把内层查询结果当作外层查询的比较条件)#不用order by 来查询最新的商品select goods_id,goods_name from goods where goods_id = (select max(goods_id) from goods)#取出每个栏目下最新的产品(goods_id唯一)select cat_id,goods_id,goods_name from goods where goods_id in(select max(goods_id) from goods group by cat_id)2、from型子查询(把内层的查询结果供外层再次查询)#用子查询查出挂科两门及以上的同学的平均成绩思路:#先查出哪些同学挂科两门以上select name,count(*) as gk from stu where score <60 having gk >=2#以上查询结果,我们只要名字就可以了,所以再取一次名字select name from (select name,count(*) as gk from stu having gk >=2) as t#找出这些同学了,那么再计算他们的平均分select name,avg(score) from stu where name in (select name from (select name,count(*) as gk from stu having gk >=2) as t) group by name3、exists型子查询(把外层查询结果拿到内层,看内层的查询是否成立)#查询哪些栏目下有商品,栏目表category,商品表goodsselect cat_id,cat_name from category where exists(select * from goods where goods.cat_id = category.cat_id)欢迎分享,转载请注明来源:内存溢出
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