How to use joins to cross check data from multiple tables - sql

Question

I got a few tables which I need to query to crosscheck information.
All tables are in the same database.
First table is named Confirmedsitesv2 and contains a column named sites.
Sedond table is named Standardwithmail and contains three columns. sites, username and mail.
Third table named CDDump contains alot of columns but there is only three I am intrested in. Uid, employeenddate and company.
I need to query so I get site, username and mail based on the following criteria.
Site from standardwithmail matches site in confirmedsitesv2, username from standardwithmail matches uid in CDDUmp, while the employmentenddate = 0 and company is not like %test%. Mail should not be matched with anything as it only occurs in standardwithmail but will show for all the hits from the query.
So I tryed to get my head around this with left joins for nearly two hours.
Anyone experienced who can who can explain how I should use join in this situation? I done outer joins before for totaly different case and that worked easy and fine, but can't get my head around this even after alot of time on google.
If needed I can create some fake tables and upload pictures as I can't show the real data here.

Answer 1

Please try this:
SELECT cfrsites.sites standard.username,
standard.mail
FROM Confirmedsitesv2 cfrsites,
Standardwithmail standard,
CDDump cd
where cfrsites.sites = standard.site
and standard.username = cd.Uid
If you can edit your post, add the Table structure and add some insert statements that will be helpful

Answer 2

So why mail did not work was because it's in the the big table I only used for other information, I renamed that column in standardwithmail and I ran:
select site, username, mailaddress
from Standardwithmail
left join CDDump on CDDump.uid = dbo.Standardwithmail.Username where Site in (select Site from Confirmedsitesv2) and employmentEnd like '0' and companyName not like '%test%'
order by Site;

Answer 3

Try out the following query. You don't need outer join or left join, but just inner joins since you only want matching records.
SELECT swm.username,
swm.mail
FROM standardwithmail swm
INNER JOIN confirmedsitesv2 csv2
ON swm.sites = csv2.sites
INNER JOIN cddump cdd
ON swm.username = cdd.uid
WHERE cdd.employmentenddate = 0
AND
cdd.company NOT LIKE '‰test‰'