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I'm trying to left join three tables using columns from the first and third tables as the filters. The second and third tables could have null values where I am trying to join. I want to be able to return all rows if I don't specify the second parameter (:store_number), but it only returns rows where the store_number is not null.

SELECT t1.host_name, t1.vcenter_name, t1.connection_state, t1.power_state, t2.cluster_name, t3.store_number, t3.district_number, t3.time_zone, t3.active
FROM host t1
LEFT JOIN cluster t2 ON t1.cluster_id = t2.cluster_id AND t1.vcenter_name = t2.vcenter_name
LEFT JOIN store t3 on t2.cluster_name IS NOT NULL AND t2.cluster_name = t3.store_number
WHERE t1.host_name LIKE :host_name AND t3.store_number LIKE :store_number
ORDER BY t1.host_name;

To clarify, not all hosts have clusters, and not all clusters associate to store numbers. I want to be able to return all rows even if I don't specify a store number in the parameter, but currently it only returns rows that have a store number that is not null. Passing to the parameter as %value%.

Here is what I am getting currently:

+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+
| host_name   | vcenter_name  | connection_state | power_state | cluster_name | store_number | district_number | time_zone | active |
+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+
| host1       | vcenter1      | Connected        | PoweredOn   | cluster1     | store1       | 1               | nonprod   | false  |
| host2       | vcenter1      | Connected        | PoweredOn   | cluster1     | store1       | 1               | nonprod   | false  |
| host1       | vcenter1      | Connected        | PoweredOn   | cluster2     | store2       | 2               | nonprod   | false  |
| host2       | vcenter1      | Connected        | PoweredOn   | cluster2     | store2       | 2               | nonprod   | false  |
+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+

Here is what I would like to get:

+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+
| host_name   | vcenter_name  | connection_state | power_state | cluster_name | store_number | district_number | time_zone | active |
+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+
| host1       | vcenter1      | Connected        | PoweredOn   | cluster1     | store1       | 1               | nonprod   | false  |
| host2       | vcenter1      | Connected        | PoweredOn   | cluster1     | store1       | 1               | nonprod   | false  |
| host1       | vcenter1      | Connected        | PoweredOn   | cluster2     | store2       | 2               | nonprod   | false  |
| host2       | vcenter1      | Connected        | PoweredOn   | cluster2     | store2       | 2               | nonprod   | false  |
| host1       | vcenter2      | Connected        | PoweredOn   | NULL         | NULL         | NULL            | NULL      | NULL   |
| host1       | vcenter3      | Connected        | PoweredOn   | cluster3     | NULL         | NULL            | NULL      | NULL   |
| host2       | vcenter3      | Connected        | PoweredOn   | cluster3     | NULL         | NULL            | NULL      | NULL   |
+-------------+---------------+------------------+-------------+--------------+--------------+-----------------+-----------+--------+
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  • unclear what second parameter is and what 'it is not null means'. Include sample data and expected results.
    – danblack
    Jun 12 '19 at 0:55
  • Added additional information. Jun 12 '19 at 15:49
  • Put t3.store_number LIKE :store_number in your JOIN ON criteria rather than the WHERE criteria. Being in WHERE means the the store_number of null won't match the criteria.
    – danblack
    Jun 13 '19 at 1:35
  • That worked! Thank you! If you add that as an answer, I can accept it. Jun 13 '19 at 19:13
1

Put t3.store_number LIKE :store_number in your JOIN ON criteria rather than the WHERE criteria.

Being in WHERE means the the store_number of NULL won't match the criteria however being in a LEFT JOIN, t3.* are padded in the result when the JOIN criteria isn't met.

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