How To Check If a Record in Table 1 Exist in Table 3

[bodots]

Hello Everyone...I am a new and trying to learn SQL programming. I want to check if a particular record in table 1 has already a record in table 3. Here's my table structure.

History - Table 3 Relation - Table 2 Account - Table 1
----------------- ------------------ ------------------
custID custID custAccount
custAccount CustAccount

I cannot set a relation directly from table 1 into table 3 because there is no custID column in table 1. I have to pass to table 2.

What I want to check is if the Relation.custID of Account.custAccount has already a record in History.

Thanks and regards

 

[simian336]

select a.custAccount, r.custID, r.custAccount, H.custID, H.custAccount
from Account a
join Relation r
on R.custAccount = A.custAccount
join History H
on R.custAccount = H.custAccount
and R.custID = H.custID

If H.custID, H.custAccount are null then they don't exist.

Simi