show columns from quote;
Field | Type | Null | Key | Default | Extra |
---|
id | int(8) unsigned | NO | PRI | NULL | auto_increment |
code | text | YES | | NULL | |
date | date | YES | | NULL | |
open | double | YES | | NULL | |
high | double | YES | | NULL | |
low | double | YES | | NULL | |
close | double | YES | | NULL | |
volume | bigint(20) | YES | | NULL | |
select code,max(date) as date from quote group by code;
可以找出每个 code 组里面对应的最大date.
我现在想找出每个组中,最大的date,对应的其他条字段记录,我写成下面的方式
create table b SELECT code,max(date) as date from quote group by code ;
select * from quote as a , b where a.code = b.code and a.date = b.date;
效率很低,请问,如何改进?
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