SQL inner join question

[Hunor Szombatfalvi]

Hello All,

While trying to write an sql querry I ran into the following case that i can't explain and was wondering if someone could:

run sql select count(numplan.pkid) from numplan
(count)
=======
2721

run sql select count(numplan.pkid) from numplan inner join devicenumplanmap on devicenumplanmap.fknumplan = numplan.pkid
(count)
=======
6169

Inner join is supposed to be the overlap between two sets, which means that there should be no way for the result to be bigger than any of the two sets going in

any ideas?

[Nithin Eluvathingal]

Inner Join clause in SQL Server creates a new table (not physical) by combining rows that have matching values in two or more tables.

AFAIK, you are making a table showing the count of  numplan  which has devicenumplanmap.fknumplan = numplan.pkid

2.12.0.0

[Hunor Szombatfalvi]

I figured it out, I made a fundamentally incorrect assumption, that devicenumplanmap.fknumplan has unique values, however it turns out that multiple entries in devicenumplanmap.fknumplan point to the same numplan.pkid. I can now fix this using select distinct