如何在SQL中添加变量

Question

I have a variable that I need to show it by month. This variable is a boolean and if its set True, it means that the app was installed.

Example: variable = intalled apps

In January there were 20 installed apps. In February there were 10 installed apps. In March there were 5 installed apps.

I want to show on the table all the apps that were installed (boolean = True):

January: 20

February: 20 (January) + 10 =  30

March: 20 (January) + 10 (February) + 5 (March) = 35

Does anyone know how I could do this in Mysql?

Thanks

Answer 1

You could use a subquery to group installations by month. Then you can us a variable in the outer query to calculate the cumulative sum:

select  installation_year
,       installation_month
,       installation_count
,       (@running_sum:= @running_sum + installation_count) as cumulative_sum
from    (
        select  year(installation_date) as installation_year
        ,       month(installation_date) as installation_month
        ,       count(*) as installation_count
        from    YourTable
        group by
                installation_year
        ,       installation_month
        ) as SubQueryAlias
join    (select @running_sum := 0) as InitVars
order by 
        installation_year
,       installation_month

Example at SQL Fiddle.

Answer 2

something like:

Select COUNT(*),Month 
From Apps
where installed = true
group by Month

Answer 3

If I understand correctly, it's just a simple query with an order by.

select COLUMNS_YOU_WANT from TABLE_NAME 
where YOUR_BOOLEAN == True 
order by SOME_DATE_COLUMN

Hopefully you're proficient enough in SQL to replace the sections with what you need.

Answer 4

I'm assuming that you have an "Applications" table that contains an "Installed" column and an "InstalledDate" column. If so...

SELECT Count(*)
FROM   Applications
WHERE  Installed = 1 -- Assumes a bit/boolean column.
AND    InstalledDate BETWEEN @StartDate AND @EndDate;

Scott

Answer 5

I GOT IT! I used the recursive

SELECT (select id_time from database.dim_time where id_time = a.fk_time) AS yearmonth, (select sum( if( installed in (1), 1,0)) as installed from database.facts_table where fk_time <= yearmonth ) as installed FROM database.facts_table AS a GROUP BY yearmonth ORDER BY yearmonth ASC