postgresql - Datawharehouse Fact Table Geneate -


currently, building fact table base ods tables , dimension tables. ods table

1.datewisedata

sid_date

total_impressions

2.devices(mobile phone,pc,etc)

sid_date

device_id

device_name

total_impressions

3.advertiserdata

sid_date

advertiser_id

advertiser_name

total_impressions

fact table

id

sid_date

devicesid

advertiserid

total_impressions

here, facing issue join 3 table data in single fact table. in case have 3 different total impression on each table. in fact table add single total impression. how can calculate , join then. tried different join technicians didn't find perfect solution.

please handle case

are trying build dimensional (kimball) data warehouse? if so, there changes can make.

(1) don't need datewisedata.

(2) don't need total_impressions on devices.

(3) don't need total_impressions on advertiserdata.

might suggest model should more this:

calendar (id, cal_date, cal_year, cal_month, ... ) device (id, name) advertiser (id, name) impression (calendar_id, device_id, advertiser_id, impression_count)

this assumes fact can have more 1 impression. if not correct, have known "factless fact", , table should this:

impression (calendar_id, device_id, advertiser_id)

now can run queries that, example, calculate total impressions device on given date:

select device.name,count(*)   impression        inner join device on device.id = device_id        inner join calendar on calendar.id = calendar_id  calendar.cal_date = '2016-02-08' group  device.name;

does meet requirement?

edit: respond question, below.

in case want first form of fact table:

impression (calendar_id, device_id, advertiser_id, impression_count)

and query find impressions advertiser looks this:

select advertiser.name,sum(impression_count)   impression        inner join advertiser on advertiser.id = advertiser_id        inner join calendar on calendar.id = calendar_id  calendar.cal_date = '2016-02-08' group  advertiser.name;

if attempt carry totals anywhere else end in world of pain.


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