mysql和sqlserver的order by 和group by和distinct引起的兼容性问题 max函数解决

1：SELECT * FROM T_STANDARD_SYSTEM GROUP BY SYSTEM_ID ORDER BY SYSTEM_ID

2：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)

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

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