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                ThinkChat2.0新版上線,更智能更精彩,支持會話、畫圖、視頻、閱讀、搜索等,送10W Token,即刻開啟你的AI之旅 廣告
                :-: ![](https://img.kancloud.cn/42/12/42122f743a2cda5a968ac02a6d8b3924_560x395.png) 如圖中所示,`uid = 50222`的用戶在`2022-11-22`這一天連續簽到了10次。很明顯此表沒有**唯一索引**,但是代碼方面的原因暫不考慮(不是咱寫的) ![](https://img.kancloud.cn/92/1e/921edd252fbd306eee07c0400fb223a6_850x170.png) ### 要求: 刪除重復數據,并且保留最新一條(用戶一天重復有十條,刪九留一) > PS:其實不難,由于沒有接觸過 **SQLServer**,還有其中涉及的幾個函數,所以記錄一下 ### 思路: 1. 查出所有重復簽到的數據 2. 查出重復簽到中最新的一條數據 3. 刪除 ~~~ -- 統計重復數據 SELECT convert(varchar(10), addtime,20) time, uid, COUNT(uid) count FROM wap_qda GROUP BY convert(varchar(10), addtime,20), uid HAVING count(uid) > 1 -- 重復簽到中最新的一條數據ID SELECT MAX(ID) ID FROM wap_qda GROUP BY convert(varchar(10), addtime,20), uid HAVING count(uid) > 1 -- 全部重復數據 SELECT a.* FROM wap_qda a, (SELECT convert(varchar(10), addtime,20) time, uid FROM wap_qda GROUP BY convert(varchar(10), addtime,20), uid HAVING count(uid) > 1) b WHERE convert(varchar(10), a.addtime,20) = b.time AND a.uid = b.uid -- 刪除 DELETE FROM wap_qda WHERE wap_qda.ID IN (SELECT a.ID FROM wap_qda a, (SELECT convert(varchar(10), addtime,20) time, uid FROM wap_qda GROUP BY convert(varchar(10), addtime,20), uid HAVING count(uid) > 1) b WHERE convert(varchar(10), a.addtime,20) = b.time AND a.uid = b.uid) AND wap_qda.ID NOT IN (SELECT MAX(ID) ID FROM wap_qda GROUP BY convert(varchar(10), addtime,20), uid HAVING count(uid) > 1 ) ~~~ - **CONVERT()** [CONVERT()](https://www.w3school.com.cn/sql/func_convert.asp) 函數是把日期轉換為新數據類型的通用函數 CONVERT(data_type(length),data_to_be_converted,style) *data\_type(length)* 規定目標數據類型(帶有可選的長度)。*data\_to\_be\_converted*含有需要轉換的值。*style*規定日期/時間的輸出格式。
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