Fetch last 3 month data as separate columns not rows for each user

Question

i have a mysql table \"bf_monthly_bill\" in which data against each users from another table \"bf_users\" is stored month wise.

Structure of my bf_users table is

<

Answer 1

Try this::

SELECT bu.name, 
    max(case when (bb.bill_month='Jan2k19') then bb.package_price else NULL end) as 'first_month_bill',
    max(case when (bb.bill_month='Feb2k19') then bb.package_price else NULL end) as 'second_month_bill',
    max(case when (bb.bill_month='Mar2k19') then bb.package_price else NULL end) as 'third_month_bill'
    FROM bf_users bu
    INNER JOIN bf_monthly_bill bb
    ON bu.id = bb.bf_users_id GROUP BY bu.name;

Output::

name    first_month_bill    second_month_bill   third_month_bill
ABC       500                   200                  500
DEF       300                  (null)                300
GHI       900                   542                  900
JKL      (null)                (null)                200

Here is SQLFiddle demo

Answer 2

You can try using conditional aggregation

select display_name,
       sum(case when bill_month='Jan2k19' then package_price end) as first_bill,
       sum(case when bill_month='Feb2k19' then package_price end) as second_bill,
       sum(case when bill_month='Mar2k19' then package_price end) as third_bill
from
(
   SELECT u.display_name,b.package_price,b.bill_month
   from bf_users u inner join bf_monthly_bill b on u.id=b.company_id
)A group by display_name

Answer 3

1. Use LEFT JOIN to make sure, you get complete list of companies even though there is no bill for any month.
2. You have to create n columns manually or using a script.
3. You can just do simple join, no subquery is required.
4. Use GROUP BY to generate single record per company.
5. Use CASE WHEN or IF ELSE to create n columns and pick data from relevent row only. It can be first or any row, so use aggregate function to pick data even it is at any row for a group by making other row values as NULL as aggregate function exclude null values.

SELECT 
    u.display_name,
    SUM(IF( bill_month='Jan2k19', package_price, NULL)) as first_bill,
    SUM(IF( bill_month='Feb2k19', package_price, NULL)) as second_bill,
    SUM(IF( bill_month='Mar2k19', package_price, NULL)) as third_bill
FROM bf_users u 
LEFT JOIN bf_monthly_bill b on u.id=b.company_id
GROUP BY u.display_name;