Mysql經常使用Sql

時間 2019-11-11

標籤 mysql 經常使用 sql 欄目 MySQL 简体版

原文原文鏈接

刪除表中多餘的重複記錄，重複記錄是根據單個字段（wm_classresid）來判斷，只留有wm_id最小的記錄ssr

DELETE FROM wm_classresourcesclass

WHERE wm_classresid IN (SELECT wm_classresid FROM (SELECT wm_classresid FROM wm_classresources GROUP BY wm_classresid HAVING COUNT(wm_classresid) > 1) a)

AND wm_id NOT IN ( SELECT wm_id FROM (SELECT MIN(wm_id) AS wm_id FROM wm_classresources GROUP BY wm_classresid HAVING COUNT(wm_classresid )>1) b)

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