query to get the SUM - sql

Question

Supposed I have a data of
code_table
code_id | code_no | stats |
2 60 22A3
3 60 22A3
value_table
value_no | amount_value_one | amount_value_two | amount_diff | code_no | sample_no | code_id
1 1200.00 400.00 800.00 60 90 2
1 600.00 200.00 400.00 60 100 3
1 1800.00 600.00 1200.00 60 110 2
2 1200.00 1200.00 0.00 60 110 2
2 800.00 600.00 200.00 60 90 2
2 400.00 0.00 400.00 60 100 3
What I want to happen is to get all the SUM of amount_value_two and just retain the first amount_value_one which has the value_no = 1
the output can be conclude as
amount_value_one | SUM_of_amount_value_two | amount_diff | sample_no
1200.00 1000.00 200.00 90
600.00 200.00 400.00 100
1800.00 1.800.00 0.00 110
so far i have this following query
SELECT SUM(p.amount_value_one) as value_one,
SUM(p.amount_value_two) as value_two,
SUM(p.amount_diff) as amount_diff,
p.sample_no as sampleNo FROM value_table p
INNER JOIN code_table On code_table.code_no = p.code_no
WHERE code_table.code_id = p.code_id
AND code_table.stats = '22A3'
GROUP BY p.sample_no
the query above that I used is wrong because it gets the sum of both p.amount_value_one
and p.amount_diff
its just a test query because i cant imagine what would the query will look like.

Answer 1

Assuming that you have a column that specifies the ordering, then you can use that to figure out the "first" row. Then use conditional aggregation:
SELECT SUM(CASE WHEN seqnum = 1 THEN p.amount_value_one END) as value_one,
SUM(p.amount_value_two) as value_two,
SUM(p.amount_diff) as amount_diff,
p.sample_no as sampleNo
FROM (SELECT p.*,
ROW_NUMBER() OVER (PARTITION BY p.sample_no ORDER BY <ordering column>) as seqnum
FROM value_table p
) p JOIN
code_table ct
ON ct.code_no = p.code_no AND
ct.code_id = p.code_id
WHERE ct.stats = '22A3'
GROUP BY p.sample_no