在laravel中的where子句中使用一個查詢結果的方式是什么，就像我們在SQL查詢中使用where in子句那樣？

Question

我在Laravel中編寫查詢，但它給了我錯誤提示

ErrorException：類stdClass的對象無法轉換為字符串

$subject_ids = DB::table('question_sets')
                   ->select('subject_id')
                   ->where('test_section_id','=',$testDetail->test_section_id)
                   ->distinct()
                   ->get();

$topic_ids = DB::table('topics')
                 ->select('id')
                 ->where('subject_id','=',$subject_ids)
                 ->get();

Answer 1

在下面的查詢

$subject_ids = DB::table('question_sets')
                   ->select('subject_id')
                   ->where('test_section_id','=',$testDetail->test_section_id)
                   ->distinct()->get();

您正在獲取一個集合，如果您想要一個特定的值，則可以使用first()然后執行

$subject_id = DB::table('question_sets')
                  ->select('subject_id')
                  ->where('test_section_id','=',$testDetail->test_section_id)
                  ->distinct()
                  ->pluck('name')
                  ->first();

和

$topic_ids = DB::table('topics')
                 ->select('id')
                 ->where('subject_id','=',$subject_id)
                 ->get();

或者如果要與所有$ subject_ids匹配，則應使用toArray()和whereIn

$subject_ids = DB::table('question_sets')
                   ->select('subject_id')
                   ->where('test_section_id','=',$testDetail->test_section_id)
                   ->distinct()
                   ->pluck('subject_id')
                   ->toArray();

和

$topic_ids = DB::table('topics')
                 ->select('id')
                 ->whereIn('subject_id', $subject_ids)
                 ->get();