SQL DB2 Toad - 按 ID 对两个表求和

Question

I was hoping to find the sum from two tables with columns ID and Amount, grouping by ID. My first attempt was to UNION the two tables first and then conduct a sum and group by, but I was hoping to know of a better way.

Inputs:

Table 1

ID    Amount
123   100
123   100
145   500
167   600

Table 2
ID    Amount
123   100
123   100
145   500
199   600

Output

ID    Amount
123   400
145   1000
167   600
199   600

Answer 1

You can do:

select id, sum(amount) as amount 
from (
  select id, amount from table_1
  union all
  select id, amount from table_2
) x
group by id