SQL Join to only the maximum row puzzle
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by Billy ONeal
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Published on 2010-04-08T16:25:15Z
Indexed on
2010/04/08
16:33 UTC
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Given the following example data:
Users
+--------------------------------------------------+
| ID | First Name | Last Name | Network Identifier |
+--------------------------------------------------+
| 1 | Billy | O'Neal | bro4 |
+----+------------+-----------+--------------------+
| 2 | John | Skeet | jsk1 |
+----+------------+-----------+--------------------+
Hardware
+----+-------------------+---------------+
| ID | Hardware Name | Serial Number |
+----+-------------------+---------------+
| 1 | Latitude E6500 | 5555555 |
+----+-------------------+---------------+
| 2 | Latitude E6200 | 2222222 |
+----+-------------------+---------------+
HardwareAssignments
+---------+-------------+-------------+
| User ID | Hardware ID | Assigned On |
+---------+-------------+-------------+
| 1 | 1 | April 1 |
+---------+-------------+-------------+
| 1 | 2 | April 10 |
+---------+-------------+-------------+
| 2 | 2 | April 1 |
+---------+-------------+-------------+
| 2 | 1 | April 11 |
+---------+-------------+-------------+
I'd like to write a SQL query which would give the following result:
+--------------------+------------+-----------+----------------+---------------+-------------+
| Network Identifier | First Name | Last Name | Hardware Name | Serial Number | Assigned On |
+--------------------+------------+-----------+----------------+---------------+-------------+
| bro4 | Billy | O'Neal | Latitude E6200 | 2222222 | April 10 |
+--------------------+------------+-----------+----------------+---------------+-------------+
| jsk1 | John | Skeet | Latitude E6500 | 5555555 | April 11 |
+--------------------+------------+-----------+----------------+---------------+-------------+
My trouble is that the maximum "Assigned On" date for each user needs to be selected for each individual user and used for the actual join ...
Is there a clever way accomplish this in SQL?
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