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Editorial Team
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Asked: 2026-06-12T07:34:28+00:00

I have 2 tables on 2 different databases : db1.table1 +————–+————————–+ | Username |

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I have 2 tables on 2 different databases :

db1.table1 

+--------------+--------------------------+
| Username     | Message                  |
+--------------+--------------------------+
| jamesbond    | I need some help         |
| jamesbond    | I need some help         |
| jamesbond    | I need some help         |
| jamesbond    | Mission accomplished     |
+--------------+--------------------------+

db2.table2 

+--------------------------+--------------+
| Message                  | Status       |
+--------------------------+--------------+
| I need some help         | Ok           |
| I need some help         | Ok           |
| I need some help         | Bad          |
+--------------------------+--------------+

when I do ‘INNER JOIN’ those tables using this SQL syntax :

SELECT A.Username, A.Message
SUM(CASE WHEN `status` = 'Ok' THEN 1 ELSE 0 END) AS StatOK,
SUM(CASE WHEN `status` = 'Bad' THEN 1 ELSE 0 END) AS StatBAD
FROM db1.table1 as A
INNER JOIN db2.table2 as B 
ON A.Message = B.Message
WHERE A.Username = 'jamesbond'
GROUP BY A.Username, A.Message

I got this result :

+--------------+--------------------------+--------+---------+
| Username     | Message                  | StatOK | StatBAD |
+--------------+--------------------------+--------+---------+
| jamesbond    | I need some help         | 2      | 1       |
+--------------+--------------------------+--------+---------+

how to get result like this (message without status on DB2 still appear, but the SUM result can be ZERO or NULL) :

+--------------+--------------------------+--------+---------+
| Username     | Message                  | StatOK | StatBAD |
+--------------+--------------------------+--------+---------+
| jamesbond    | I need some help         | 2      | 1       |
| jamesbond    | Mission accomplished     | NULL   | NULL    |
+--------------+--------------------------+--------+---------+
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1 Answer

  1. Editorial Team

    You need a Left Outer Join, It will get the rows from Left tables and if it doesn’t match with Right table then You’ll get NULL.

    SELECT A.Username, A.Message
SUM(CASE WHEN `status` = 'Ok' THEN 1 ELSE 0 END) AS StatOK,
SUM(CASE WHEN `status` = 'Bad' THEN 1 ELSE 0 END) AS StatBAD
FROM db1.table1 as A
LEFT OUTER JOIN db2.table2 as B 
ON A.Message = B.Message
WHERE A.Username = 'jamesbond'
GROUP BY A.Username, A.Message
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