Distinct In SQL 查询结果重复值

Question

在我的数据库中有来自同一员工的多个条目，因此我想通过识别自动编号字段来获取最新条目。但是在 eno 中使用下面的 sql 代码和 distinct 会导致重复条目。

SELECT distinct(eNo), auto_num from mc_employee 
order by auto_num

关于我做错了什么的任何线索？

Answer 1

DISTINCT 不是应用于 SELECT 子句的特定字段的函数。它更适用于所有 SELECT 子句中存在的字段。

如果你想得到最新的记录那么你可以使用ROW_NUMBER:

SELECT eNo, auto_num
FROM (
   SELECT eNo, auto_num,
          ROW_NUMBER() OVER (PARTITION BY eNo ORDER BY auto_num DESC) AS rn 
   from mc_employee ) AS t
WHERE t.rn = 1
ORDER BY auto_num

Answer 2

尝试以下查询：

SELECT eNo,auto_num 
FROM
( SELECT eNo, auto_num, ROW_NUMBER() OVER(PARTITION BY eNo ORDER BY auto_num DESC) as RN
  FROM mc_employee
)T
WHERE RN=1

Answer 3

最简单的方法是TOP(1) WITH TIES ... ORDER BY ROW_NUMBER() OVER ()

SELECT TOP(1) WITH TIES eNo, auto_num
FROM mc_employee
ORDER BY ROW_NUMBER() OVER (PARTITION BY eNo ORDER BY auto_num DESC)

Answer 4

这里还有一个子select解决方案：

SELECT distinct(dist.eNo), (select max(auto_num) from mc_employee i where i.eNo=dist.eNo) auto_num
from mc_employee dist
order by auto_num

Distinct In SQL 查询结果重复值

Distinct In SQL Query resulting duplicate Values

sql

sql-server

sql-server-2014-express