Question

我有以下查询。

select entity_id ,parent_id,name as label , url_key as name from magento_catalog_category_flat_store_1 where entity_id IN(
SELECT distinct T1.parent_id
FROM magento_catalog_category_flat_store_1 T1 
INNER JOIN magento_catalog_category_flat_store_1 as T2 ON 
           T1.entity_id = T2.parent_id
RIGHT JOIN sohyper_region_activity as T3 on 
           T2.entity_id = T3.activity_id)

由于IN子句，上述查询会降低性能。谁能告诉我如何在这个查询中用JOIN替换IN子句？

感谢。

Answer 1

一般

SELECT ...
FROM Table1
WHERE col1 IN (SELECT col2 FROM ...)

可以转换为：

SELECT ...
FROM Table1 t1
JOIN (SELECT DISTINCT col2 FROM ...) t2
ON t1.col1 = t2.col2

Answer 2

试试这个

SELECT Tab1.entity_id ,Tab1.parent_id,Tab1.name As Label , Tab1.url_key As Name 
FROM magento_catalog_category_flat_store_1 Tab1 JOIN
(
SELECT distinct T1.parent_id
FROM magento_catalog_category_flat_store_1 T1 
INNER JOIN magento_catalog_category_flat_store_1 as T2 ON 
           T1.entity_id = T2.parent_id
RIGHT JOIN sohyper_region_activity as T3 on 
           T2.entity_id = T3.activity_id
) Tab2 ON Tab1.entity_id = Tab2.parent_id

Answer 3

显然没有经过测试！

WITH (
SELECT distinct T1.parent_id
FROM magento_catalog_category_flat_store_1 T1 
INNER JOIN magento_catalog_category_flat_store_1 as T2 ON 
           T1.entity_id = T2.parent_id
RIGHT JOIN sohyper_region_activity as T3 on 
           T2.entity_id = T3.activity_id)
) T0
select entity_id ,parent_id,name as label , url_key as name from 
magento_catalog_category_flat_store_1 T1 
INNER JOIN magento_catalog_category_flat_store_1 as T2 ON 
           T1.entity_id = T2.parent_id
RIGHT JOIN sohyper_region_activity as T3 on 
           T2.entity_id = T3.activity_id
INNER JOIN T0
ON T0.entity_id = magento_catalog_category_flat_store_1.entity_id

如何在sql中用JOIN替换IN子句？

3 个答案: