Find duplicates in MS SQL table - sql

Question

I know that this question has been asked several times but I still cannot figure out why my query is returning values which are not duplicates. I want my query to return only the records which have identical value in the column Credit. The query executes without any errors but values which are not duplicated are also being returned. This is my query:
Select
_bvGLTransactionsFull.AccountDesc,
_bvGLAccountsFinancial.Description,
_bvGLTransactionsFull.TxDate,
_bvGLTransactionsFull.Description,
_bvGLTransactionsFull.Credit,
_bvGLTransactionsFull.Reference,
_bvGLTransactionsFull.UserName
From
_bvGLAccountsFinancial Inner Join
_bvGLTransactionsFull On _bvGLAccountsFinancial.AccountLink =
_bvGLTransactionsFull.AccountLink
Where
_bvGLTransactionsFull.Credit
IN
(SELECT Credit AS NumOccurrences
FROM _bvGLTransactionsFull
GROUP BY Credit
HAVING (COUNT(Credit) > 1 ) )
Group By
_bvGLTransactionsFull.AccountDesc, _bvGLAccountsFinancial.Description,
_bvGLTransactionsFull.TxDate, _bvGLTransactionsFull.Description,
_bvGLTransactionsFull.Credit, _bvGLTransactionsFull.Reference,
_bvGLTransactionsFull.UserName, _bvGLAccountsFinancial.Master_Sub_Account,
IsNumeric(_bvGLTransactionsFull.Reference), _bvGLTransactionsFull.TrCode
Having
_bvGLTransactionsFull.TxDate > 01 / 11 / 2014 And
_bvGLTransactionsFull.Reference Like '5_____' And
_bvGLTransactionsFull.Credit > 0.01 And
_bvGLAccountsFinancial.Master_Sub_Account = '90210'

Answer 1

That's because you're matching on the credit field back to your table, which contains duplicates. You need to isolate the rows that are duplicated with ROW_NUMBER:
;WITH CTE AS (
SELECT *, ROW_NUMBER() OVER(PARTITION BY CREDIT ORDER BY (SELECT NULL)) AS RN
FROM _bvGLTransactionsFull)
Select
CTE.AccountDesc,
_bvGLAccountsFinancial.Description,
CTE.TxDate,
CTE.Description,
CTE.Credit,
CTE.Reference,
CTE.UserName
From
_bvGLAccountsFinancial Inner Join
CTE On _bvGLAccountsFinancial.AccountLink = CTE.AccountLink
WHERE CTE.RN > 1
Group By
CTE.AccountDesc, _bvGLAccountsFinancial.Description,
CTE.TxDate, CTE.Description,
CTE.Credit, CTE.Reference,
CTE.UserName, _bvGLAccountsFinancial.Master_Sub_Account,
IsNumeric(CTE.Reference), CTE.TrCode
Having
CTE.TxDate > 01 / 11 / 2014 And
CTE.Reference Like '5_____' And
CTE.Credit > 0.01 And
_bvGLAccountsFinancial.Master_Sub_Account = '90210'
Just as a side note, I would consider using aliases to shorten your queries and make them more readable. Prefixing the table name before each column in a join is very difficult to read.

Answer 2

I trust your code in terms of extracting all data per your criteria. With this, let me have a different approach and see your script "as-is". So then, lets keep first all the records in a temp.
Select
_bvGLTransactionsFull.AccountDesc,
_bvGLAccountsFinancial.Description,
_bvGLTransactionsFull.TxDate,
_bvGLTransactionsFull.Description,
_bvGLTransactionsFull.Credit,
_bvGLTransactionsFull.Reference,
_bvGLTransactionsFull.UserName
-- temp table
INTO #tmpTable
From
_bvGLAccountsFinancial Inner Join
_bvGLTransactionsFull On _bvGLAccountsFinancial.AccountLink =
_bvGLTransactionsFull.AccountLink
Where
_bvGLTransactionsFull.Credit
IN
(SELECT Credit AS NumOccurrences
FROM _bvGLTransactionsFull
GROUP BY Credit
HAVING (COUNT(Credit) > 1 ) )
Group By
_bvGLTransactionsFull.AccountDesc, _bvGLAccountsFinancial.Description,
_bvGLTransactionsFull.TxDate, _bvGLTransactionsFull.Description,
_bvGLTransactionsFull.Credit, _bvGLTransactionsFull.Reference,
_bvGLTransactionsFull.UserName, _bvGLAccountsFinancial.Master_Sub_Account,
IsNumeric(_bvGLTransactionsFull.Reference), _bvGLTransactionsFull.TrCode
Having
_bvGLTransactionsFull.TxDate > 01 / 11 / 2014 And
_bvGLTransactionsFull.Reference Like '5_____' And
_bvGLTransactionsFull.Credit > 0.01 And
_bvGLAccountsFinancial.Master_Sub_Account = '90210'
Then remove the "single occurrence" data by creating a row index and remove all those 1 time indexes.
SELECT * FROM (
SELECT
ROW_NUMBER() OVER (PARTITION BY Credit ORDER BY Credit) AS rowIdx
, *
FROM #tmpTable) AS innerTmp
WHERE
rowIdx != 1
You can change your preference through PARTITION BY <column name>.
Should you have any concerns, please raise it first as these are so far how I understood your case.
EDIT : To include those credits that has duplicates.
SELECT
tmp1.*
FROM #tmpTable tmp1
RIGHT JOIN (
SELECT
Credit
FROM (
SELECT
ROW_NUMBER() OVER (PARTITION BY Credit ORDER BY Credit) AS rowIdx
, *
FROM #tmpTable) AS innerTmp
WHERE
rowIdx != 1
) AS tmp2
ON tmp1.Credit = tmp2.Credit