Nested Select with ZF2 - zend-framework2

Question

Trying to get a nested select using Zend\Db\Sql\Select and can't see anything at all in the documentation or on google.
Wanting to do something like this:
SELECT
table1.*,
(SELECT x,y,z FROM table2 WHERE table2.a = table1.a) as b
FROM table1
Without the nested select, it would look something like this:
$select = new Zend\Db\Sql\Select;
$select
->columns(array(
'*'
))
->from('table1')
ZF1 looked about creating a subSelect item and then adding it as an Expression inside the list of columns but in ZF2 it complains about an Expression needing to be a string.
Edit: The nested-select needs to be as a column as I end up with multiplied rows when using GROUP BY on same column name. This is the correct query I'm trying to get into Zend\Db\Sql\Select:
SELECT
users.id,
(SELECT count(explorations.id) FROM explorations WHERE user_id = users.id) as total_explorations,
count(villages.id)
FROM
users
INNER JOIN
villages
on (villages.user_id = users.id)
GROUP BY
users.id

Answer 1

Ralph Schindler has a repository of different DB patterns that he has specifically implemented in Zend\Db. Here's one for subselects: https://github.com/ralphschindler/Zend_Db-Examples/blob/master/example-20.php
The content is this:
<?php
/** #var $adapter Zend\Db\Adapter\Adapter */
$adapter = include ((file_exists('bootstrap.php')) ? 'bootstrap.php' : 'bootstrap.dist.php');
refresh_data($adapter);
use Zend\Db\Sql;
use Zend\Db\ResultSet\ResultSet;
$sql = new Sql\Sql($adapter);
$subselect = $sql->select();
$subselect->from('artist')
->columns(array('name'))
->join('album', 'artist.id = album.artist_id', array())
->where->greaterThan('release_date', '2005-01-01');
$select = $sql->select();
$select->from('artist')
->order(array('name' => Sql\Select::ORDER_ASCENDING))
->where
->like('name', 'L%')
->AND->in('name', $subselect);
$statement = $sql->prepareStatementForSqlObject($select);
$result = $statement->execute();
$rows = array_values(iterator_to_array($result));
assert_example_works(
count($rows) == 2
&& $rows[0]['name'] == 'Lady Gaga'
&& $rows[1]['name'] == 'Linkin Park'
);
Basically, you can use one select as the value of the predicate of another select.

Answer 2

I would suggest you restructure you SQL query. I'm not sure which database you are using, but if you are using MySQL, the COUNT function can use the DISTINCT keyword. This way you don't count the duplicated ids. I've adjusted your SQL query to what I would use, this way you eliminate the need for inner select.
SELECT
users.id,
COUNT(DISTINCT explorations.id) AS total_explorations,
COUNT(DISTINCT villages.id) AS total_villages
FROM users
INNER JOIN villages ON villages.user_id = users.id
INNER JOIN explorations ON explorations.user_id = users.id
GROUP BY users.id
I haven't run this query, but I'm sure it should work and give you the result you want. Hopefully I'm not misunderstanding your situation. Below is the equivalent Zend Framework 2 select.
$select = $sql->select('users');
$select->columns(array('id'));
$select->join('villages',
'villages.user_id = users.id',
array(
'total_villages' => new Expression("COUNT(DISTINCT villages.id)")
)
);
$select->join('explorations',
'explorations.user_id = users.id',
array(
'total_explorations' => new Expression("COUNT(DISTINCT explorations.id)")
)
);

Answer 3

What you are describing is defined as a JOIN. There are some different join scenarios and i will not cover the differences of them, but the most commons would be INNER JOIN or LEFT JOIN.
And this is indeed to be found inside the ZF2-Documentation of Zend\Db\Sql#Join
The Query would look like this:
Select
t1.*,
t2.field1,
t2.field2,
t2.field3
FROM
tablename1 t1,
tablename2 t2
WHERE
t1.field = t2.field
Looking at the Documentation of ZF2-Documentation of Zend\Db\Sql#Join, i think the Select would look like this:
$select = new \Zend\Db\Sql\Select();
$select->columns(array(
'id',
'title',
// List ALL Columns from TABLE 1 - * is bad/slow!
), true)->from(array(
't1' => 'tablename1'
))->join(
'tablename2',
'id = t1.id',
array(
'username',
'email',
// List ALL Columns from TABLE 2 u want to select
),
$select::JOIN_INNER
)
Another i think: If you don't use the columns() you'd SELECT * but for your own sake, start writing good queries ;) Have more control over your code!
Can't promise that this code works, since i don't use Zend\Db on my own, but using the Documentation on the right point should get you running nonetheless.

Answer 4

I Hope I am getting your problem correctly...
Still not upgraded myself to ZF2 but this is one of the way you can create a nested Select statement in ZF1 if you are using MVC architecture(try it in ZF2 also).
$table1 = new table1();
$table1->select()->from('table1',array('*',
'b' => '(SELECT x,y,z FROM table2 WHERE table2.a = table1.a)',
));
Update:
Got back to this after your comment and realized that the code I've written would not work as you will not be able select multiple columns from another table into a single column(i.e x,y,z in b).
But yes it would work in case you have to perform some agg. function on the other table which gives out a single column. e.g.
$table1 = new table1();
$table1->select()->from('table1',array('*',
'b' => '(count (*) FROM table2 WHERE table2.a = table1.a)',
));
So this would work.
This way you can get some of the columns with some function performed on them.
And the rest of the columns from the other table(table2) you can get using a join.