mysql left join查询取1个_mysql left join复杂1点的查询方法示例

mysql left join复杂一点的查询方法示例

SELECT a.id,b.series_id,COUNT(b.id) cnt FROM (SELECT id FROM lib_brand_series WHERE 2>1 AND brand_id=1 AND category_id=5 AND STATUS=1) a LEFT JOIN (SELECT id,series_id FROM lib_product_index a WHERE 2>1 AND small_category_id = 252 AND brand_id = 1) b ON a.id = b.series_id GROUP BY a.id

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优化后sql有一点点修改：

SELECT a.id,COUNT(b.id) FROM lib_brand_series a LEFT JOIN (SELECT * FROM lib_product_index WHERE small_category_id = 252 AND brand_id = 1)b ON a.id = b.series_id WHERE a.brand_id=1 AND a.category_id=5 AND a.STATUS=1 GROUP BY a.id

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如图所示：

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