Sql 使用GROUP BY仅显示每个用户最新更新的行

我一直很难找到语法来执行

groupby

只显示每个用户的最新

ups.db\u LastUpdate

行（BY

db\u UserId

）

输出（将有几百个用户，但你明白了这一点）：

可能类似于

GROUP BY ups.dbUserId，MAX（db\u LastUpdate）

---

感谢您的帮助

使用

行号

：

;WITH CTE AS
(
    SELECT  up.db_FirstName, 
            up.db_LastName, 
            up.db_UserId, 
            ups.db_Initials, 
            ups.db_LastUpdate,
            RN = ROW_NUMBER() OVER(PARTITION BY up.db_UserId ORDER BY ups.db_LastUpdate DESC)
    FROM tblUserProfile up
    INNER JOIN tblUserSel ups
            ON ups.db_Code = up.db_UserId
    WHERE ups.db_UserTech = 'U'
)
SELECT *
FROM CTE
WHERE RN = 1;

正如注释中所指出的，您可以使用

MAX

，然后加入您的表：

;WITH CTE AS
(
    SELECT  up.db_UserId, 
            MAX(ups.db_LastUpdate) MaxLastUpdate
    FROM tblUserProfile up
    INNER JOIN tblUserSel ups
            ON ups.db_Code = up.db_UserId
    WHERE ups.db_UserTech = 'U'
    GROUP BY up.db_UserId
)
SELECT B.*
FROM CTE A
INNER JOIN tblUserSel B
    ON A.db_UserId = B.db_Code
    AND A.MaxLastUpdate = B.db_LastUpdate;

---

但是您需要知道，如果同一用户存在一个日期相同的行，那么您将得到这两行。

如果您的表有一个唯一的ID列，我通常会这样处理这种情况：

WITH LastEdit AS (
    SELECT ups.db_Code, ups.db_Initials, ups.db_LastUpdate
    FROM tblUserSel ups
    WHERE ups.db_UserTech = 'U' AND ups.ID = (
        SELECT TOP 1 ID
        FROM tblUserSel upsn
        WHERE ups.db_Initials = upsn.db_Initials
        ORDER BY upsn.db_LastUpdate DESC
    )
)
SELECT up.db_FirstName, up.db_LastName, up.db_UserId, le.db_Initials, le.db_LastUpdate 
FROM tblUserProfile up
    INNER JOIN LastEdit le
        ON le.db_Code = up.db_UserId

---

按任何列分组，。。。拥有MAX（db_LastUpdate）您认为添加

MAX（）

解决方案以及显示其他选项会有帮助吗？@Zane好的，好的，我在回答中添加了该选项您和您的CTE:）@Zane是的，我喜欢他们；-）

;WITH CTE AS
(
    SELECT  up.db_UserId, 
            MAX(ups.db_LastUpdate) MaxLastUpdate
    FROM tblUserProfile up
    INNER JOIN tblUserSel ups
            ON ups.db_Code = up.db_UserId
    WHERE ups.db_UserTech = 'U'
    GROUP BY up.db_UserId
)
SELECT B.*
FROM CTE A
INNER JOIN tblUserSel B
    ON A.db_UserId = B.db_Code
    AND A.MaxLastUpdate = B.db_LastUpdate;

WITH LastEdit AS (
    SELECT ups.db_Code, ups.db_Initials, ups.db_LastUpdate
    FROM tblUserSel ups
    WHERE ups.db_UserTech = 'U' AND ups.ID = (
        SELECT TOP 1 ID
        FROM tblUserSel upsn
        WHERE ups.db_Initials = upsn.db_Initials
        ORDER BY upsn.db_LastUpdate DESC
    )
)
SELECT up.db_FirstName, up.db_LastName, up.db_UserId, le.db_Initials, le.db_LastUpdate 
FROM tblUserProfile up
    INNER JOIN LastEdit le
        ON le.db_Code = up.db_UserId