Drupal db_select - How to combine UNION with LIMIT properly? - database

Question

I'm trying to get content from database divided by category. I want strictly max 4 entries of type "people" and three other entries of type "organization".
I tried to do it like that:
$query = db_select('node', 'n')
->fields('n', array('title','type'))
->fields('i', array('field_image_fid'))
->fields('f', array('uri'))
->condition('n.title', '%'. db_like($keys) . '%', 'LIKE')
->condition('type', array('people'))
->range(0,4);
$query->leftJoin('field_data_field_image', 'i', 'i.entity_id = n.nid');
$query->leftJoin('file_managed', 'f', 'f.fid = i.field_image_fid');
$query2 = db_select('node', 'n')
->fields('n', array('title','type'))
->fields('i', array('field_image_fid'))
->fields('f', array('uri'))
->condition('n.title', '%'. db_like($keys) . '%', 'LIKE')
->condition('type', array('organization'))
->range(0,4);
$query2->leftJoin('field_data_field_image', 'i', 'i.entity_id = n.nid');
$query2->leftJoin('file_managed', 'f', 'f.fid = i.field_image_fid');
$query->union($query2, 'UNION');
$result = $query
->execute();
The problem is that this query is returning only the first three occurrences of people or organization combined. So if there are three people returned by the query, I will not be able to see any organization.
I also tried something like this:
$query = db_query('
SELECT p.title,p.type
FROM node as p
WHERE p.type = :type
LIMIT 4'
, array(':type' => 'people',':type1' => 'organization'))->fetchAll();
$query2 = db_query('
SELECT o.title,o.type
FROM node as o
WHERE o.type = :type1
LIMIT 4'
, array(':type' => 'people',':type1' => 'organization'))->fetchAll();
$query->union($query2, 'UNION');
or like this:
$result = db_query('
SELECT title,type
FROM {node}
WHERE type = :type
LIMIT 4
UNION ALL
SELECT title,type
FROM {node}
WHERE type = :type1
LIMIT 4'
, array(':type' => 'people',':type1' => 'organization'))->fetchAll();
But these two approaches are only returning the 4 people and no organizations, I mean never..
Thank you if you can help!

Answer 1

Union statement in query its actually get record from first query and merge result record of first query to second query result record.
For example first case don't used limit in query of union its giving all record.
$query1 = db_select('node', 'n')
->fields('n', array('nid','title','type'))
->condition('type', array('people'));
$query2 = db_select('node', 'n')
->fields('n', array('nid','title','type'))
->condition('type', array('organization'));
$query = Database::getConnection()
->select($query1->union($query2))
->fields(NULL, array('nid','title', 'type'))
->orderBy('nid');
$result = $query->execute()->fetchAll();
From above query it get records from first query append before records of second query
As per the you example If you wanted to get 4 records from people content type and 3 record from organizations content type
used following query to solve your issue
$query1 = db_select('node', 'n')
->fields('n', array('nid','title','type'))
->condition('type', array('people'))
->range(0,4);
$query2 = db_select('node', 'n')
->fields('n', array('nid','title','type'))
->condition('type', array('organization'));
->range(0,7);
$query = Database::getConnection()
->select($query1->union($query2))
->fields(NULL, array('nid','title', 'type'))
->orderBy('nid');
$result = $query->execute()->fetchAll();