我有这些表，rolls和rollsout。我想执行左外连接。滚动|type|height|weight|Rate|-------------------------|RP|2ft|200|100||RP|2ft|200|100||RP|2ft|200|100||LD|2ft|100|130|推出|type|height|weight|Rate|-------------------------|RP|2ft|200|100||RP|2ft|200|100|SUMing、JOINing和GROUPing后的预期输出==>|type|height|SUM(rolls.weight)|SUM