Laravel 5.X: Use of SubQuery | Sub Query in Where Condition

Laravel 5.X: Use of Sub-query | Sub Query in Where Condition. It's very important. Below is an sample example how we can use sub-query in our application.

$test_data = Employee::from((new Employee())->getTable() . " AS entity")

OR

$test_data = DB::table((new Employee())->getTable() . " AS entity")
    ->whereIn("entity.id", function($q) {
        $q->select("entity.id");
        $q->from((new Employee())->getTable() . " AS entity");
        $q->join((new Supervisor())->getTable() . " AS user", "user.id", "=", "entity.sup_id");
        $q->whereNotNull("entity.sup_id");
        $q->where("user.first_name", "like", "%E%");
    })
    ->select("entity.id", "entity.type")
    ->limit(5)
    ->get();

And will generate below SQL:

SELECT
  `entity`.`id`,
  `entity`.`type`
FROM `employee` AS `entity`
WHERE `entity`.`id` IN (
  SELECT `entity`.`id`
  FROM `employee` AS `entity` INNER JOIN `users` AS `user` ON `user`.`id` = `entity`.`sup_id`
  WHERE `entity`.`sup_id` IS NOT NULL AND `user`.`first_name` LIKE '%E%'
)
LIMIT 5