58 lines
989 B
Markdown
Executable File
58 lines
989 B
Markdown
Executable File
# 数据去重方法
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> SQL Server 数据去重常用方法
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## 方法一：使用 DISTINCT
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```sql
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SELECT DISTINCT * FROM TableName
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```
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## 方法二：临时表去重
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```sql
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BEGIN TRAN
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-- 1. 选中不重复的数据到临时表
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SELECT DISTINCT * INTO #temp FROM DataSyncStationSX
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-- 2. 删除原表数据
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DELETE FROM DataSyncStationSX
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-- 3. 从临时表导回
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INSERT INTO DataSyncStationSX SELECT * FROM #temp
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-- 4. 删除临时表
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DROP TABLE #temp
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COMMIT
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```
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## 方法三：ROW_NUMBER 去重
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```sql
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-- 删除重复数据，保留最新一条
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DELETE FROM TableName
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WHERE ID IN (
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SELECT ID FROM (
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SELECT ID, ROW_NUMBER() OVER (PARTITION BY duplicate_column ORDER BY created_time DESC) AS rn
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FROM TableName
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) t
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WHERE rn > 1
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)
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```
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## 方法四：查找重复数据
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```sql
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-- 查找重复记录
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SELECT column1, column2, COUNT(*) as cnt
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FROM TableName
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GROUP BY column1, column2
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HAVING COUNT(*) > 1
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```
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---
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> ⚠️ 执行删除前请先备份数据！
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