SQL 查询 - 只计算满足特定条件的月份

Question

I am having a trouble writing a sql query...basically I have about a million or so rows (cards) with transactions divided into columns - months (12 months).

So each row shows how big transaction did the card do each month. Now the problem is - I am trying to select only the cards who have met a certain condition only 7 months during the year.

The condition is each month (duration 7 months) they spend more then 5 000 eur.

I just do not know what is the function that would show me the resulst for the 7 months..I have wrote the whole query but for the whole year, now I need to narrow it down just to the 7 months, but do not know how...I have "googled" all over. Important - the 7 months doesnt need to be in a row - it can be any month during the year. Could anybody help me with this?

Tank you, K.

Answer 1

You should fix your data model to store months in rows, not in columns.

Here is a solution that uses union all in a subquery to generate such a structure on the fly, then aggregates and filters with a having clause:

select card
from (
    select card, month_1 spent from mytable
    union all select card, month_2 from mytable
    -- ... one "union all" statement per column ...
    union all select card, month_12 from mytable
) t
group by card
having sum(case when spent > 5000 then 1 end) = 7

This assumes a data structure like:

card      -- primary key
month_1   -- amount spent during the 1stmonth
month_2   -- amount spent during the 2nd month
...
month_2   -- amount spent during the 12th month