How to get data for below scenario? - sql-server

Question

I have 4 tables.
Employee:
Id|emp_start_date|Public_id|
01|00-00-00 |001
02|00-00-00 |002
Person:
Id|Public_id|name|...
01|001 |aaaa|..
02|002 |bbbb|...
pay_info:
public_id|current_pay_year
001|2015
002|2015
Ni_table:
public_id|Ni_letter_code|Niable_pay|ni_a|ni_b|ni_c|ni_d|year
001 |A |890 |12 | 12 | 0 | 0 |2015
002 |A |500 |14 |14 |0 | 0 |2015
002 |A |600 |14 |14 |0 | 0 |2015
002 |B |400 |13 | 13 |0 |0 |2015
002 |B |500 |13 | 13 |0 |0 |2015
I want to get the Sum of niable_pay and all other columns by using ni_letter_code for the year 2015.
I want to get all the employees details for current pay year.
But When the employee has two ni letter code, then he should have 2 row for them.
Each row should have the addition value for the respective ni_code.
Expected output:
01|A| 890|12|12|0|0|2015
02|A|1100|25|28|0|0|2015
02|B| 900|26|26|0|0|2015
My query:
select
e.id,
NI.Ni_letter_code,
SUM(NI.Niable_pay),
SUM(ni_a),
SUM(ni_b),
SUM(ni_c),
SUM(ni_d),
ni.year
from
employee e
JOIN person P ON e.id=P.id
INNER JOIN pay_info PI ON PI.public_id = E.public_id
INNER JOIN Ni_table NI ON NI.public_id = E.public_id
AND NI.year = PI.current_pay_year

Answer 1

You seem to think that by stating
select
e.id,
NI.Ni_letter_code,
SUM(NI.Niable_pay),
SUM(ni_a),
SUM(ni_b),
SUM(ni_c),
SUM(ni_d),
ni.year
you get a result record per e.id, NI.Ni_letter_code and ni.year along with the desired sums.
This is not the case. SQL doesn't aggregate by non-aggregated columns implicitely. You must make the aggregation group explicit with GROUP BY. So in order to get one result record per e.id, NI.Ni_letter_code and ni.year you'd add:
group by e.id, NI.Ni_letter_code, ni.year
at the end of your query:
select
e.id,
NI.Ni_letter_code,
SUM(NI.Niable_pay),
SUM(ni_a),
SUM(ni_b),
SUM(ni_c),
SUM(ni_d),
ni.year
from
employee e
JOIN person P ON e.id=P.id
INNER JOIN pay_info PI ON PI.public_id = E.public_id
INNER JOIN Ni_table NI ON NI.public_id = E.public_id
AND NI.year = PI.current_pay_year
group by e.id, NI.Ni_letter_code, ni.year;