按 DESC 订购的替代方案

Question

此 sql 查询获取记录总共需要 9 分钟..

select top 1 checkdate 
from BTHI1
where CUSTOMERID = 'AUTOMO' and recordtype='T'
order by checkdate desc

还有其他方法可以减少查询时间吗？

Answer 1

对于这个查询：

select top 1 checkdate 
from BTHI1
where CUSTOMERID = 'AUTOMO' and recordtype = 'T'
order by checkdate desc

您想要 BTH1(CUSTOMERID, recordtype, checkdate DESC) 上的索引。前两列可以按任意顺序排列。

注意你也可以这样写：

select max(checkdate) 
from BTHI1
where CUSTOMERID = 'AUTOMO' and recordtype = 'T';

Alternative for order by DESC