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distinct在sqlserver中不能解决的去重问题max groupby_MySQL

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Release: 2016-06-01 13:28:59
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distinct在sqlserver中不能解决的去重问题max groupby

 

1:SELECT * FROM T_STANDARD_SYSTEM GROUP BY SYSTEM_ID ORDER BY SYSTEM_ID2:SELECT *,COUNT(DISTINCT system_id) FROM T_STANDARD_SYSTEM GROUP BY SYSTEM_ID ORDER BY SYSTEM_IDselect * FROM T_STANDARD_SYSTEM WHERE system_Id IN(SELECT MAX(system_id) FROM T_STANDARD_SYSTEM GROUP BY system_id)
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上面第二条是解决mysql不同版本不兼容问题,第一条在某些版本中是能用的。但是不规范在sqlserver中两条都不能用。

SELECT SYSTEM_ID,MAX(SYSTEM_NAME) SYSTEM_NAME,MAX(SYSTEM_ABRIDGE) SYSTEM_ABRIDGE,MAX(SUB_SYSTEM_ID) SUB_SYSTEM_ID,MAX(SUB_SYSTEM_NAME) SUB_SYSTEM_NAME, MAX(CUSTOM_SYSTEM_ID) CUSTOM_SYSTEM_ID,MAX(CUSTOM_SYSTEM_NAME) CUSTOM_SYSTEM_NAME FROM T_STANDARD_SYSTEM GROUP BY SYSTEM_ID ORDER BY SYSTEM_ID
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以上这条是解决sqlserver和mysql上面那个不兼容问题的。

Oracle提供一个rowId可以通过子查询方便的解决上述去重问题

 

distinct在sqlserver中不能解决的去重问题max groupby_MySQL
distinct在sqlserver中不能解决的去重问题max groupby_MySQL

 

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