mysql table data rows to column

Question

I'm trying to achieve yearly data as pivot, this is my query

SELECT
    month(te.topup_date) as month,
    sum(CASE WHEN year(te.topup_date) = '2015' THEN te.topup_amount+ tp.topup_amount END) as '2015',
    sum(CASE WHEN year(te.topup_date) = '2016' THEN te.topup_amount+ tp.topup_amount END) as '2016'
from te_daily_topup as te
inner join tp_daily_topup as tp on year(te.topup_date) = year(tp.topup_date) 
where year(te.topup_date) between '2015' and '2016'
group by year(te.topup_date), month(te.topup_date)

The result from the above query

month | 2015 | 2016
--------------------
1     | 123  | 
2     | 2343 |
1     |      |234
2     |      |7667

The result I'm looking for is below:

month | 2015 | 2016
--------------------
1     | 123  | 234
2     | 2343 | 7667

help me to modify this query..

Answer 1

Just remove year() from the GROUP BY:

select month(te.topup_date) as month,
       sum(case when year(te.topup_date) = 2015 then te.topup_amount + tp.topup_amount end) as `2015`,
       sum(case when year(te.topup_date) = 2016 then te.topup_amount + tp.topup_amount end) as `2016`
from te_daily_topup te inner join
     tp_daily_topup tp
     on year(te.topup_date) = year(tp.topup_date) 
where year(te.topup_date) between 2015 and 2016
group by month(te.topup_date);

Note: Do not use single quotes for integer constants nor for column aliases. Only use single quotes for string and date constants.