General Sql Question

[samporras]

Hey guys...I've got a question for ya.

 

I'm trying to create a suppression process so I can then create a list of people i want to email. So far I have 2 tables. Table A contains email addresses and another field I call suppression_type (this field will get it's value based on different types of suppression that i do). Table B contains a running lists of people that opt not to receive an email. Anyways, basically I'm running a query that matches on email addresses and then updates the suppression_type field in table A.

 

I am currently doing this using a sub query that looks like this:

 

>update TableA
set suppression_type = 1
where rtrim(ltrim(Email) in (select ltrim(rtrim(Email)) from TableB)
and suppression_type is null

 

I tried running counts using this sub query and then using another query that has an inner join (should do the same thing right?). I noticed that the counts were higher using an inner join. Here's the query I ran:

 

>select count(*)
from TableA as A
inner join	
TableB as B on
A.Email = B.Email
Where A.suppression_type is null

 

Can anyone explain the difference between these two and why they would be off?

 

Thanks so much for your help!

 

-Sam