two syntax problems with join and left-join in the same query - mysql

Question

I have this code to create a collection:
$rank_entities_by_capacity = Entity::join('entity_capacitytypes', function($q){
$q->on('entitys_id', '=', 'entities.id');
$q->where('capacitytypes_id','=', '23');
})->
leftJoin('user_attitudes', function($q){
$q->on('entity_id', '=', 'entities.id');
$q->where('item_type', '=', 'entity');
})
->selectRaw('entities.*, SUM(user_attitudes.importance) AS importance')
->groupBy('entities.id')
->orderBy('importance', 'desc')
->take(6)
->get();
First problem:
1052 Column 'entity_id' in on clause is ambiguous:
[2015-01-01 13:22:28] production.ERROR: FATAL DATABASE ERROR: 500 = SQLSTATE[23000]: Integrity constraint violation: 1052 Column 'entity_id' in on clause is ambiguous (SQL: select entities.*, SUM(user_attitudes.importance) AS importance from entities inner join entity_capacitytypes on entity_id = entities.id and capacitytypes_id = 23 left join user_attitudes on entity_id = entities.id and item_type = entity group by entities.id order by importance desc limit 6) [] []
I traded over an hour for finding a trick to bypass the problem:
I was forced to change column name in table entity_capacitytypes from entity_id (it was causing problems) to entitys_id just in order to avoid this error.
Now my database names are not consistent. Any other way to avoid the error?
Problem 2:
If I add this part to the query, and try to use a previously perfectly working variable in the where line
join('entity_capacitytypes', function($q){
$q->on('entitys_id', '=', 'entities.id');
$q->where('capacitytypes_id','=', $capacity);
})->
I get this error:
Undefined variable: capacity
How make the variable work?
My solution: avoidance again.
I ould't fix join, so I used a relation defined in Capacitytype model:
public function entities()
{
return $this->belongsToMany('Entity', 'entity_capacitytypes', 'capacitytypes_id', 'entitys_id');
}
and instead using join, I accessed Entity from another model
$rank_entities_by_capacity = Capacitytype::find($capacity)->entities()->
leftJoin('user_attitudes', function($q){
$q->on('entity_id', '=', 'entities.id');
$q->where('item_type', '=', 'entity');
})
->selectRaw('entities.*, SUM(user_attitudes.importance) AS importance')
->groupBy('entities.id')
->orderBy('importance', 'desc')
->take(6)
->get();
To do:
make the variable work in join

Answer 1

Problem 1
To fix the "ambiguous column" problem you only need to specify the full column name including the table
entity_capacitytypes.entity_id instead of only entity_id
Problem 2
To use a local variable like $capacity inside a closure (aka anonymous function) you need to inject them with use
join('entity_capacitytypes', function($q) use ($capacity){
$q->on('entitys_id', '=', 'entities.id');
$q->where('capacitytypes_id','=', $capacity);
})