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Incremental and decremental count based on a date - Mailing list pgsql-novice

From koimoi
Subject Incremental and decremental count based on a date
Date
Msg-id 1519161114631-0.post@n3.nabble.com
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Responses Re: Incremental and decremental count based on a date  ("David G. Johnston" <david.g.johnston@gmail.com>)
List pgsql-novice
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Name Start_date end_date
aaa  01/02/2017  05/03/2017
bbb  03/05/2017  07/07/2017
ccc  02/01/2017  10/09/2017
I want to write a query that calculates the number of people who exist in
the DB in a certain month/year.

Answer:

Jan 2017  1
Feb 2017  2
Mar 2017  3
Apr 2017  3
May 2017  2 (one person - aaa ,ended in May 2017)
Jun 2017  2
Jul 2017  1 (bbb ended in July 2017)
How do I write a PSQL query to get the desired output?

Thanks.



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