Suppose the following configuration:
When there is info to be stored, there will be records added to the info table. I can easily get a nice overview of the number of records for each user like:
mysql> SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId ORDER BY nbr_entries DESC;
+-----------+-------------+
| userId | nbr_entries |
+-----------+-------------+
| 3987 | 2254 |
| 11220 | 1922 |
...
Now, my question: I would like to have each userId to be looked up in Table 1 (generic), so that my query result would like like:
+-----------+-----------+-------------+
| name | userId | nbr_entries |
+-----------+-----------+-------------+
| Peter | 3987 | 2254 |
| Walter | 11220 | 1922 |
...
Any idea how to achieve this? Thanks in advance.
You could use JOIN
SELECT b.name,userid,COUNT(*) as nbr_entries FROM info a
inner join generic b on a.userid=b.id
GROUP BY b.name,userId
ORDER BY nbr_entries DESC;
You can use subquery
& JOIN
SELECT t1.name, t2.userId , t2.nbr_entries
FROM generic t1
JOIN
(SELECT userId ,COUNT(*) as nbr_entries FROM info GROUP BY userId) t2
ON t1.userId = t2.userId ORDER BY t2.nbr_entries DESC;
Use a LEFT JOIN:
SELECT g.name, g.id as userId, COUNT(i.userId) as nbr_entries
FROM generic g
LEFT JOIN info i ON i.userId = g.id
GROUP BY g.id
ORDER BY nbr_entries DESC
This way you will also include users who has no info entries (yet) and get 0
as nbr_entries
.
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