Duplicate Columns with Inner Join

Duplicate columns with inner Join

You have duplicate columns, because, you're asking to the SQL engine for columns that they will show you the same data (with SELECT dealing_record.* and so on) , and then duplicates.

For example, the transaction_type.transaction_type_id column and the dealing_record.transaction_type_id column will have matching rows (otherwise you won't see anything with an INNER JOIN) and you will see those duplicates.

If you want to avoid this problem or, at least, to reduce the risk of having duplicates in your results, improve your query, using only the columns you really need, as @ConradFrix already said. An example would be this:

SELECT 
    dealing_record.Name
    ,shares.ID
    ,shares.Name
    ,transaction_type.Name
    ,transaction_type.ID
FROM 
    shares 
    INNER JOIN shares ON shares.share_ID = dealing_record.share_id
    INNER JOIN transaction_type ON transaction_type.transaction_type_id = dealing_record.transaction_type_id;

How to remove duplicate columns from join in SQL

Since you are querying the table with '*', you will always get all the columns in both tables. In order to omit this column, you will have to manually name all columns you DO want to query. To address your other need, you need to simply insert a dummy column to each clause in the union query. Below is an example that should work to allow for what you want -

SELECT customer.customerid, customer.customername, customer.customeraddress, newspapername, magazinename, enddate, publishedby 
FROM customer
INNER JOIN
(select  customerid, newspapername, null Magazinename, enddate, n.publishedby 
 from newspapersubscription ns, newspaper n 
 where publishedby in(select publishedby 
                    from newspaper 
                    where ns.newspapername = n.NewspaperName)
UNION
select  customerid, null newspapername, Magazinename, enddate, m.publishedby 
from magazinesubscription ms, magazine m 
 where publishedby in(select publishedby 
                    from magazine 
                     where ms.Magazinename = m.MagazineName))
on customer.customerid = customerid
ORDER BY customer.customerid;

SQL: Remove duplicate columns when joining tables with large number of columns

If the only duplicate columns are the JOIN columns, you can fix this with USING:

SELECT *
FROM TABLEA A INNER JOIN
     TABLEB B 
     USING (id)
WHERE <SOME_CONDITION>;

Remove duplicate columns after using join on in sql

Solution 1:
Specify the column names like this

SELECT
    t1.Name, t1.ItemNum, t1.TicketNum
FROM (
    SELECT TOP 100
        Name, ItemNum, TicketNum
    FROM [dbo].[dd]
) t1 
INNER JOIN (
    SELECT TOP 100
        TicketNum, ItemNum
    FROM [dbo].[dd]
) t2 ON t1.ItemNum = t2.ItemNum
    AND t1.TicketNum = t2.TicketNum

Solution 2:

SELECT t1.* FROM (
    SELECT TOP 100
        Name, ItemNum, TicketNum
    FROM [dbo].[dd]
) t1 
INNER JOIN (
    SELECT TOP 100
        TicketNum, ItemNum
    FROM [dbo].[dd]
) t2 ON t1.ItemNum = t2.ItemNum
    AND t1.TicketNum = t2.TicketNum

mysql: duplicate column name on join with subquery

In the subselect of your join, you are selecting a.controlno and by t.* t.controlno.
You should provide an alias for one of the selected columns. In your case a.controlno. This is necessary, because the table aliases of the inner select are lost, when accessing it from the outer one.

The statement below should work, if there aren't any other duplicate column names in test and the set of used columns from applicant.

SELECT sp.testno, sp.companyid, st.* 
FROM sponsor AS sp
LEFT JOIN
(
    SELECT a.sponsorempno, (CASE WHENt.companyid IS NULL OR t.companyid = '' THEN'aa' ELSE t.companyid END) agncy, a.controlno as a_controlno, a.tnpl, t.* 
    FROM applicant AS a
    LEFT JOIN
        test AS t
    ON a.controlno = t.controlno 
) AS st
ON sp.testno = st.testno

SQL problems duplicate column name using inner join and missing right parenthesis

For the first query, the GROUP BY is inconsistent with the SELECT. Plus, the SUM() expression is not correct:

SELECT ACCOUNT.BillNo, UPPER(Non_resident) as Non_resident, 
       SUM(ConsumptionCharge + SupplyCharge) AS TotalCharge
FROM BILL JOIN
     ACCOUNT
     ON ACCOUNT.BILLNO = BILL.BILLNO
WHERE Non_resident = Upper('Yes') AND to_char(CreatedDate,'mm') = '09'
GROUP BY ACCOUNT.BILLNO;

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