Mysql query to find sum of fields with same column value

I have a table like this

我有一张这样的桌子

id |  invent_id         |   order
 1 | 95948214           | 70
 2 | 46018572           | 30
 3 | 46018572           | 20
 4 | 46018572           | 50
 5 | 36025764           | 60
 6 | 36025764           | 70
 7 | 95948214           | 80
 8 | 95948214           | 90
id |  in