sql - 从数量和ID、总重量计算的SQL命令

Question

表：订购产品

orderid   quantity       weight
-----------------------------------
4           5             0.1
4           2             0.5
5           3             2.5
5           7             0.9

1) 使用以下 SQL 命令，可以正确计算总重量，但忽略产品数量。如何扩展我的 SQL 命令来查询产品数量？

select orderid, sum (weight) as totalweight from orderproducts group by orderid

现在我有 ORDERID 4 的值（总重量）=> 0.6

必须正确 => 1.5

2）另外，我希望SQL命令“WHERE”（其中other_table.status =“finish”）从另一个表扩展。它也不起作用。:-(

select orderid, sum (weight) as totalweight from orderproducts where other_table.status = "finish" group by orderid

Answer 1

询问：

SELECT orderid,
       SUM(weight*quantity) AS totalweight
FROM orderproducts AS a
JOIN othertable AS b ON (b.orderid=b=id)
WHERE b.status = "finish"
GROUP BY orderid

Answer 2

你可以试试这个：

1）产品数量：

select orderid,sum (amount) as totalamount, sum (weight) as totalweight 
   from orderproducts group by orderid

2）除非您在其中放置子查询，否则您不能将其他表放入当前查询中表的 where 子句中。试试这个：

select orderid, sum (weight) as totalweight from orderproducts where orderid in 
   (select orderid from other_table where other_table .status = "finish")
group by orderid

Answer 3

1)

select orderid,sum (amount) as totalamount, sum (weight) as totalweight from orderproducts group by orderid

2）你必须使用加入

  select orderid, sum (weight*quantity) as totalweight from orderproducts as a join othertable AS b on (b.orderid=b=id) where b.status = "finish" group by orderid