SQLSTATE [23000]：完整性约束违规：1052 order order中的'created_at'列不明确Laravel 5.5

Question

I just don't know what's wrong with my code and why it produces this error

SQLSTATE[23000]: Integrity constraint violation: 1052 Column 'created_at' in order clause is ambiguous (SQL: select * from processes inner join bags on processes . bag_id = bags . id where bags . type = Recyclable and date( processes . created_at ) = 2018-09-18 00:00:00 order by created_at desc limit 1) and here's my code

$bag = Bagcollect::join('bags', 'bagcollects.bag_id', '=', 'bags.id')
        ->select('bags.type')
        ->where('bagcollects.bag_id', $request->input('bag_id'))
        ->first();

   //this query produce error
    $processexist = Process::join('bags', 'processes.bag_id', '=', 'bags.id')
        ->where('bags.type', $bag->type)
        ->whereDate('processes.created_at', Carbon::today())
        ->latest()
        ->first();

Answer 1

You'll need to specify, in latest() the full column. latest('process.created_at') or instead of using latest() use a custom orderBy.

Answer 2

Thats because you are querying the 'created_at' column from two tables. You have to specify wich colums you need, for example:

$processexist = Process::join('bags', 'processes.bag_id', '=', 'bags.id')
        ->select('bags.column1', 'bags.columns2')
        ->where('bags.type', $bag->type)
        ->whereDate('processes.created_at', Carbon::today())
        ->latest()
        ->first();