Finding and Replacing Duplicates With Correct Data in MySQL - mysql

Question

I have the following table with duplicate family IDs but different number of family members:
tbl_family
+------------+--------------+---------+
| familyID | Members | Location|
+------------+--------------+---------+
| 100 | 3 | xyz |
| 100 | 4 | xyz |
| 101 | 1 | abc |
| 101 | 2 | abc |
| 102 | 5 | efg |
| 103 | | hij |
+------------+--------------+---------+
I also have a second table where we verified the correct count of family members for the duplicates
tbl_verifier
+------------+--------------+---------+
| familyID | Members | Location|
+------------+--------------+---------+
| 100 | 3 | xyz |
| 101 | 2 | abc |
+------------+--------------+---------+
I want to create a view in mysql which will display the families without duplicates and maintain the row with the verified count of family members. The results should look as follows:
tbl_results
+------------+--------------+---------+
| familyID | Members | Location|
+------------+--------------+---------+
| 100 | 3 | xyz |
| 101 | 2 | abc |
| 102 | 5 | efg |
| 103 | | hij |
+------------+--------------+---------+
I am breaking the problem into several steps. I want to first select all those with matching Members then those with null Members
/* Step 1: Select only those that are matching family members count in
verifier and family */
select *
from tbl_family f
inner join
tbl_verifier v
ON f.familyID = v.familyID
WHERE f.Members = v.Members;
/* Step 2 : Select only those that have null number of rooms*/
select *
from tbl_family f
left join
tbl_verifier v
ON f.familyID = v.familyID
WHERE f.Members is null
Now am a bit stuck on how to proceed further.

Answer 1

Use UNION All to merge two result sets
select *
from tbl_family f
inner join tbl_verifier v ON f.familyID = v.familyID
and f.Members = v.Members
union all
select * from tbl_family f
left join tbl_verifier v ON f.familyID = v.familyID and and f.Members = v.Members
where v.familyID is null

Answer 2

how that sounds? I think it works
SELECT f.*
FROM tbl_family f, tbl_verifier v
WHERE (f.familyID = v.familyID AND f.Members = v.Members)
OR f.familyID NOT IN (SELECT familyID FROM tbl_verifier)

Answer 3

Use UNION ALL for your case, but it is better to add a location filter for same.
; with cte as (
select tbl_family.family_id, tbl_family.Members, tbl_family.location
from tbl_family
inner join tbl_verifier ON tbl_family.familyID = tbl_verifier.familyID
and tbl_family.Members = tbl_verifier.Members and tbl_family.Location = tbl_verifier.Location
union all
select tbl_family.family_id, tbl_family.Members, tbl_family.location
from tbl_family
left join tbl_verifier ON tbl_family.familyID = tbl_verifier.familyID
where tbl_family.Members is null
)
Select * from cte order by family_id

Answer 4

UNION ALL seems like a reasonable solution. The big question is how to get one row out of the first table if there are multiple rows.
Here is one method that uses MAX():
select v.familyID, v.Members, v.Location
from tbl_verifier v
union all
select f.familyID, max(f.Members), f.Location
from tbl_family f
where not exists (select 1
from tbl_verifier v
where v.familyId = f.familyId
);
Your question is unclear as to whether families can be in multiple locations. If so, you need to include location in the correlation clause.

Answer 5

From the different answers posted above, i was able to come up with the following script which worked
; with cte as (select f.familyID,
f.Members,
f.Location
from tbl_family f
inner join tbl_verifier v ON f.familyID = v.familyID
and f.Members = v.Members
union all
select f.familyID,
f.Members,
f.Location from tbl_family f
left join tbl_verifier v ON f.familyID = v.familyID
where f.Members is NULL
)
SELECT * INTO temp1 FROM cte
SELECT * FROM tbl_family WHERE familyID NOT IN (SELECT familyID FROM temp1)
UNION ALL
SELECT * FROM temp1
ORDER BY familyID