SQL根据Trasact表中的值从主表中选择差异项 [英] Sql Select disctince entries from Master Table Depending on Values in Trasact Table

问题描述

你好，

我不是SQL专业人士，所以伙计们.我需要您的帮助.
我可能在这里基本知识..但是请帮忙..

我有2个表，即Master(用户)和Transaction(logEntries).

与usrSrNo(用户索引)链接.日志条目具有事务日志.

现在，我想基于logDateTime显示不同的用户.

根据我的知识，如果我查询，

Hello,

I am not a PRO with SQL, so guys.. I need you help.
I might be laking in basic knowledge here.. but plz help..

I have 2 tables, Master(users) and Transaction(logEntries).

Linked with usrSrNo (index for Users). Log Entries have Transaction logs.

Now I want to Display Distinct Users, based on the logDateTime Desendingly.

As per My Knowledge if I query,

SELECT DISTINCT u.usrName,l.logDateTime FROM users u
JOIN logEntries l on u.usrSrNo = l.usrSrNo
ORDER BY l.logDateTime DESC

返回我的用户列表，并按LogDateTime降序排序，但不区分大小写.如何获得独特的列表?

请帮助.

Nik

Returns me user listing Sorted according to LogDateTime descending, but they are not distict. How can I Get distinct listing?

Plz Help.

Nik

推荐答案

我认为您需要选择最高日期，以使其每位用户返回一个日期.我不知道max是否可用于日期? group by子句是另一回事，请按用户选择日期最高的Nd组.

I think you need to select the top date, to make it return one date per user. I dont know if max works for dates ? A group by clause is tge other thing, select the highest date Nd group by user.

您要在用户名上设置DISTINCT，然后在logDateTime上设置.

您可以按用户名分组，然后在logDateTime上放置一个不同的名称.

You are setting DISTINCT on username and then on logDateTime.

You can group by username and then put a distinct on logDateTime.

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