fetching duplicate tuples in Oracle using SQL - sql

Question

Here are the two table structures
I have two tables where I am trying to fetch some duplicate records based on some condition like where a.fname=b.fname and a.phone_no<>b.phone_no
But also I need to include other column 'address' which is in table 2 and introduce the same condition for duplicate checking for address as well.
SELECT
"Fname"||' '||"Lname" AS "Customer_Name",
COUNT(*) AS "Countof"
FROM "S_CONTACT" A
WHERE EXISTS (
SELECT 1
FROM "S_CONTACT" B
WHERE A."PHONE" != B."PHONE"
AND A."Fname" = B."Fname"
AND A."EMAIL"=B."EMAIL"
AND A."Lname"=B."Lname"
AND "DOB" IS NULL
)
GROUP BY "Fname","Lname","EMAIL"
HAVING count(*) >1;
The above sql gives me a list of customers with duplicate names and email.
But I do not know how to introduce the column address in this sql which is from different table t2

Answer 1

If you are trying to find duplicates in one table:
select c.fname, c.lname, c.email
from contacts c
group by c.fname, c.lname, c.email
having min(c.phone) <> max(c.phone);
If you want to count null as a different value, then use:
having min(c.phone) <> max(c.phone) or count(c.phone) <> count(*)
You can do the same thing on the second table:
select c.fname, c.lname, c.email
from second_table c
group by c.fname, c.lname, c.email
having min(c.address) <> max(c.address) or count(c.address) <> count(*)
If you need the results in the same result set, then use union or union all or some similar mechanism.