laravel where raw automaticaly add is null - sql

Question

i have this code where i need to join transactions with transaction_sell_lines and transactions with purchase_lines. Then purchase_lines and transaction_sell_lines both has variation_id. I need to join those variation_id to variations table.
Transaction::leftJoin('purchase_lines as pl', 'transactions.id', '=', 'pl.transaction_id')
->leftJoin('transaction_sell_lines as sl', 'transactions.id', '=', 'sl.transaction_id')
->join('variations as v', function ($query) {
$query->where(DB::raw("CONCAT(COALESCE(sl.variation_id, ''), COALESCE(pl.variation_id, ''))"));
}, '=', 'v.id')
and when i checked the query using DB::enableQueryLog(); for some reason laravel automatically add is null even though i did not mention it anywhere. i could use whereNotNull() but the result still are not the same. the code could be seen below
from `transactions` left join `purchase_lines` as `pl` on `transactions`.`id` = `pl`.`transaction_id`
left join `transaction_sell_lines` as `sl` on `transactions`.`id` = `sl`.`transaction_id`
inner join `variations` as `v` on CONCAT(COALESCE(sl.variation_id, ''), COALESCE(pl.variation_id, '')) is null
how do i achieve this sql
from transactions LEFT JOIN purchase_lines as pl on pl.transaction_id = transactions.id
LEFT JOIN transaction_sell_lines as sl ON sl.transaction_id = transactions.id
LEFT JOIN variations as v on v.id = CONCAT(COALESCE(sl.variation_id,''),COALESCE(pl.variation_id,''))

Answer 1

I would suggest that you replace
$query->where(DB::raw("...")
with the whereRaw-function instead:
Transaction::leftJoin('purchase_lines as pl', 'transactions.id', '=', 'pl.transaction_id')
->leftJoin('transaction_sell_lines as sl', 'transactions.id', '=', 'sl.transaction_id')
->join('variations as v', function ($query) {
$query->whereRaw("CONCAT(COALESCE(sl.variation_id, ''), COALESCE(pl.variation_id, ''))");
}, '=', 'v.id')

Answer 2

you are using Advanced Join Clauses the wrong way ...
join with closure should take a Illuminate\Database\Query\JoinClause instance which allows you to specify constraints on the "join" clause, so the constraints should be in that function:
you can replace:
->join('variations as v', function ($query) {
$query->where(DB::raw("CONCAT(COALESCE(sl.variation_id, ''), COALESCE(pl.variation_id, ''))"));
}, '=', 'v.id')
with:
->join('variations as v', function ($query) {
$query->where(DB::raw("CONCAT(COALESCE(sl.variation_id, ''), COALESCE(pl.variation_id, ''))=v.id"));
})