本篇文章給大家介紹mysql怎么刪除重復(fù)數(shù)據(jù)。有一定的參考價值，有需要的朋友可以參考一下，希望對大家有所幫助。

sku對應(yīng)的重量表,應(yīng)該一個sku_id 對應(yīng)唯一 一條重量數(shù)據(jù)，由于程序錯誤導(dǎo)致出現(xiàn)一樣的冗余數(shù)據(jù)。只保留一條，其他的刪除。

假設(shè)表名：weight

查詢有重復(fù)數(shù)據(jù)的列表

SELECT sku_id,COUNT(id) FROM weight GROUP BY sku_id HAVING COUNT(sku_id) > 1

查詢重復(fù)數(shù)據(jù)里面每個最小的id

SELECT min(id) FROM weight   GROUP BY sku_id HAVING COUNT(sku_id) > 1

查詢?nèi)サ糁貜?fù)數(shù)據(jù)最小id的其他數(shù)據(jù)

SELECT id,sku_id FROM weight WHERE sku_id IN(     SELECT sku_id FROM weight   GROUP BY sku_id HAVING COUNT(sku_id) > 1)AND id NOT IN(     SELECT MIN(id) FROM weight   GROUP BY sku_id HAVING COUNT(sku_id) > 1)

刪除去掉重復(fù)數(shù)據(jù)最小id的其他數(shù)據(jù)

DELETE FROM weight WHERE sku_id IN(     SELECT sku_id FROM weight   GROUP BY sku_id HAVING COUNT(sku_id) > 1)AND id NOT IN(     SELECT MIN(id) FROM weight   GROUP BY sku_id HAVING COUNT(sku_id) > 1)

原因是：刪除這個表的同時又查詢了這個表，查詢這個表的同時又去刪除了這個表，可以理解為死鎖。mysql不支持這種刪除查詢同一張表的操作

錯誤代碼： 1093You can't specify target table 'weight' for update in FROM clause

解決辦法如下：把要刪除的數(shù)據(jù)查詢出來做為一個第三方表，然后篩選刪除。

DELETE FROM `weight` WHERE sku_id IN(     SELECT sku_id FROM (SELECT sku_id FROM `weight` GROUP BY sku_id HAVING COUNT(sku_id) > 1) table1)AND id NOT IN (     SELECT id FROM (SELECT MIN(id) AS id FROM `weight` GROUP BY sku_id HAVING COUNT(sku_id) > 1) table2)

更新也和上面操作原理相同。

推薦學(xué)習(xí)：《mysql視頻教程》