sql - 如何优化这个查询？

Question

价格 ID id_stock 价格 日期

**stocks**
id
stock_name
active

现在我必须为每个具有 MAX(prices.date) > 15 天(我必须通过的日期)的股票设置 stocks.active=0 )

这是我的查询，但是非常非常慢!!!

update stocks set stocks.active=0 where stocks.id IN (

SELECT prices.id_stock 
FROM prices
GROUP BY prices.id_stock
HAVING datediff('2010-08-17', MAX( prices.date )) > 15

)

如何优化？

非常感谢!

Answer 1

UPDATE  stocks
SET     active = 0
WHERE   DATEDIFF('2010-08-17',
        (
        SELECT  MAX(prices.date)
        FROM    prices
        WHERE   id_stock = stocks.id
        )) > 15

在价格(id_stock，日期)上创建索引