244 TP5子查询，手册里面有

表名也可以是一个子查询

$subsql = Db::table('think_work')
->where('status',1)
->field('artist_id,count(id) count')
->group('artist_id')
->buildSql();

Db::table('think_user')
->alias('a')
->join([$subsql=> 'w'], 'a.artist_id = w.artist_id')
->select();