Union of two tables in Zend 2 - mysql

Question

I want to union two tables with where clause in zf2:-
table1 app_followers
table2 app_users
where condition could be anything
and order by updated_date.
Please let me know the query for zend 2.
Thanks..

Answer 1

Using UNION is ZF2:
Using ZF2 dedicated class Combine Zend\Db\Sql\Combine
new Combine(
[
$select1,
$select2,
$select3,
...
]
)
A detailed example which uses combine is as follows:
$select1 = $sql->select('java');
$select2 = $sql->select('dotnet');
$select1->combine($select2);
$select3 = $sql->select('android');
$selectall3 = $sql->select();
$selectall3->from(array('sel1and2' => $select1));
$selectall3->combine($select3);
$select4 = $sql->select('network');
$selectall4 = $sql->select();
$selectall4->from(array('sel1and2and3' => $selectall3));
$selectall4->combine($select4);
$select5 = $sql->select('dmining');
$selectall5 = $sql->select();
$selectall5->from(array('sel1and2and3and4' => $selectall4));
$selectall5->combine($select5);
which is equivalent to the normal SQL query for UNION:
SELECT * FROM java
UNION SELECT * from dotnet
UNION SELECT * from android
UNION SELECT * from network;
UNION SELECT * from dmining;
I hope it helps.

Answer 2

I wanted to do a similar task and spent a lot of time while to figure out how to do that in the right way.
The idea with Laminas\Db\Sql\Combine is really well but you cannot apply the ordering to this object and as the result, it's useless in this case.
Finally, I ended up with the next code:
$skill = $sql->select('skill');
$language = $sql->select('language');
$location = $sql->select('location');
$occupation = $sql->select('occupation');
$skill->combine($language);
$language->combine($location);
$location->combine($occupation);
$combined = (new Laminas\Db\Sql\Select())
->from(['sub' => $skill])
->order(['updated_date ASC']);
However, it's a bit messy with parentheses. If it's a matter for you, please check this comment on Github, but on MySQL id doesn't matter, not sure about other databases.