Question

当我使用这个查询时，一切都很好。 5结果为0.3587秒。

SELECT `prod_combined`.`sku`, `prod_combined`.`titel`, `prod_combined`.`preis_vk`, 
`prod_combined`.`link` 
FROM `prod_combined` 
WHERE 
(
   prod_combined.sku IN 
       (
       SELECT 
       prod_combined.sku FROM 
       (
           SELECT prod_combined.sku FROM prod_billiger 
           INNER JOIN
           prod_combined ON prod_combined.sku = prod_billiger.sku 
           WHERE rangGesamt = 1 
           AND prod_combined.aktiv = 1 
       ) q 
       JOIN prod_combined ON prod_combined.sku = q.sku)
) 
AND (aktiv = 1)
LIMIT 0,5

但是当我使用此查询时，它会运行大约3分钟。

SELECT `prod_combined`.`sku`, `prod_combined`.`titel`, `prod_combined`.`preis_vk`, 
`prod_combined`.`link` 
FROM `prod_combined` 
WHERE 
(
   prod_combined.sku IN 
       (
       SELECT 
       prod_combined.sku FROM 
       (
           SELECT prod_combined.sku FROM prod_billiger 
           INNER JOIN
           prod_combined ON prod_combined.sku = prod_billiger.sku 
           WHERE rangGesamt = 1 
           AND prod_combined.aktiv = 1 
       ) q 
       JOIN prod_combined ON prod_combined.sku = q.sku)
) 
AND (aktiv = 1)

我想做什么：获取所有首位产品（prod_billiger.rangGesamt）。我在“prod_billiger”表中获得此信息。其他产品信息来自prod_combined。

有没有办法，加快速度？我是否需要推翻整个查询？

此致 chucky2305

Answer 1

这样的事情对你有用吗？

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link
FROM prod_combined AS pc 
WHERE pc.sku IN (
    SELECT sku
    FROM prod_billiger
    WHERE rangGesamt = 1
)
AND pc.aktiv=1

我添加了prod_combined（prod_combined AS pc）的同义词，只是为了使select语句更加简洁。

如果您的表很小，或者您有rangGesamt和/或aktiv的索引，这将很快运行。

Answer 2

重写您的查询会让我：

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined pc   
WHERE 
(
   pc.sku IN
       (
       SELECT 
       pc2.sku FROM
       (
           SELECT pc2.sku FROM 
           prod_billiger  pb
           INNER JOIN prod_combined pc2 ON pc2.sku = pb.sku
           WHERE pb.rangGesamt = 1
           AND pc2.aktiv = 1 
       ) q 
       JOIN prod_combined pc3 ON pc3.sku = q.sku
        )
) 
AND pc.aktiv = 1
;

，这可能与以下内容相同：

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined  pc
WHERE pc.sku IN (
       SELECT q.sku 
       FROM (
           SELECT pc2.sku FROM 
           prod_billiger  pb
           INNER JOIN prod_combined pc2 ON pc2.sku = pb.sku
           WHERE pb.rangGesamt = 1
           AND pc2.aktiv = 1
           ) q
        )
AND pc.aktiv = 1
        ;

可以进一步简化为：

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined  pc
WHERE EXISTS (
       SELECT *
          FROM prod_billiger  pb
          INNER JOIN prod_combined pc2 ON pc2.sku = pb.sku 
          WHERE pb.rangGesamt = 1 AND pc2.aktiv = 1
          AND pc.sku = pb.sku;
        )
AND pc.aktiv = 1
        ;

如果“sku”是prod_combined的主键，则子查询甚至可以进一步减少，只包含“prod_billiger”。

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined  pc
WHERE EXISTS (
       SELECT *
          FROM prod_billiger  pb
          WHERE pc.sku = pb.sku;
          AND pb.rangGesamt = 1 AND pc2.aktiv = 1
        )
AND pc.aktiv = 1
        ;

或多或少等同于：

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined  pc
WHERE pc.sku IN (
       SELECT sku
       FROM prod_billiger  pb
       WHERE pb.rangGesamt = 1 
       )
AND pc.aktiv = 1
        ;

如果sku也是prod_billiger的主要（或候选）键，事情甚至可以进一步减少到：

SELECT pc.sku, pc.titel, pc.preis_vk, pc.link pc
FROM prod_combined  pc
JOIN prod_billiger  pb ON pc.sku = pb.sku
WHERE pb.rangGesamt = 1
AND pc.aktiv = 1
        ;

执行时间溢出，无限制执行时

2 个答案: