How to Find the Latest Login Date and Value for Each User in SQL?

SQL query: Get the last recorded date and value of each user

The user's login record is stored in the database, and the task is to retrieve the latest login date and its corresponding value for each different user. The following table shows the table containing this data, with fields including username, date, and value:

**用户名**	**日期**	**值**
brad	2010年1月2日	1.1
fred	2010年1月3日	1.0
bob	2009年8月4日	1.5
brad	2010年2月2日	1.2
fred	2009年12月2日	1.3

SQL query to retrieve the latest record date and value for each user

Here are two ways to retrieve the latest record date and value for each user:

Method 1: Use self-connection

This classic approach utilizes a self-join to match the table to itself (based on username) and uses the MAX() aggregate function to retrieve the maximum date for each user:

<code class="language-sql">SELECT t.username, t.date, t.value
FROM MyTable t
INNER JOIN (
    SELECT username, MAX(date) AS MaxDate
    FROM MyTable
    GROUP BY username
) tm ON t.username = tm.username AND t.date = tm.MaxDate;</code>

Method 2: Use window function (if supported)

Window functions provide a more efficient alternative that avoids the duplicate record problem caused by equal dates. This method uses the ROW_NUMBER() function to operate on a result set partitioned by username and sorted by date in descending order:

<code class="language-sql">SELECT x.username, x.date, x.value
FROM (
    SELECT username, date, value,
        ROW_NUMBER() OVER (PARTITION BY username ORDER BY date DESC) AS _rn
    FROM MyTable 
) x
WHERE x._rn = 1;</code>

These queries will produce the following results, showing each user's most recent login date and value:

**用户名**	**日期**	**值**
brad	2010年2月2日	1.2
fred	2010年1月3日	1.0
bob	2009年8月4日	1.5

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