Question

价格 ID id_stock 价钱日期

**stocks**
id
stock_name
active

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

这是我的查询，但它非常慢!!!

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

)

如何优化它？

非常感谢你！

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prices (id_stock, date)

上创建索引

Answer 2

我有时会发现重写IN条款，因为EXISTS改善了问题......

UPDATE stocks SET stocks.active=0
    WHERE EXISTS (SELECT prices.id_stock 
                      FROM prices
                      WHERE prices.id_stock = stocks.id
                      GROUP BY prices.id_stock
                      HAVING datediff('2010-08-17', MAX( prices.date )) > 15);

Answer 3

Update stocks
Set active = 0
Where Exists    (
                Select 1
                From prices
                Where prices.id_stock = stocks.Id
                Having Max(prices.date) < DateAdd( '2010-08-17', Interval -15 Day)
                )

如何优化此查询？

3 个答案: