本文轉載自:http://blog.diginfos.com/index.php?r=article/view&id=126
此處以某消費記錄表(consume_record)爲例,SQL語句如下:
DELETE consume_record
FROM
consume_record,
(
SELECT
min(id) id,
user_id,
monetary,
consume_time
FROM
consume_record
GROUP BY
user_id,
monetary,
consume_time
HAVING
count(*) > 1
) t2
WHERE
consume_record.user_id = t2.user_id
and consume_record.monetary = t2.monetary
and consume_record.consume_time = t2.consume_time
AND consume_record.id > t2.id;
SQL語句分析:
1、查詢出重複記錄形成一個集合(臨時表t2),集合裏是每種重複記錄的最小ID
(SELECT min(id) id, user_id, monetary, consume_time FROM consume_record GROUP BY user_id, monetary, consume_time HAVING count(*) > 1 ) t2
2、關聯<判斷重複基準的字段
consume_record.user_id = t2.user_id and consume_record.monetary = t2.monetary and consume_record.consume_time = t2.consume_time
3、根據條件,刪除原表中id大於t2中id的記錄
DELETE consume_record FROM ... WHERE ... AND consume_record.id > t2.id;
測試效果:
圖一爲刪除前總記錄數45541,圖二爲刪除操作、從45541條記錄中刪除2800條重複記錄用時0.09秒,圖三爲刪除後總記錄數。貼上測試表,如有需要的小夥伴,下載導入即可進行測試。consume_record.sql
如下語句,用於SQL server對AccountEmail賬號信息去重:
DELETE [FSDBtemp].[dbo].[CusUsers]
FROM [FSDBtemp].[dbo].[CusUsers],
(
SELECT
min(cuid) cuid,
[AccountEmail]
FROM
[FSDBtemp].[dbo].[CusUsers]
GROUP BY
[AccountEmail]
HAVING
count(*) > 1
) t2
WHERE
[FSDBtemp].[dbo].[CusUsers].AccountEmail = t2.AccountEmail
AND [FSDBtemp].[dbo].[CusUsers].cuid > t2.cuid