Duplicate Count rows and Duplicate Delete Rows

Duplicate Count rows

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we will see how to find count of all the duplicate records in the table. Following query demonstrates usage of GROUP BY, HAVING, ORDER BY in one query and returns the results with duplicate column and its count in descending order.

SELECT YourColumn, COUNT(*) TotalCount
FROM YourTable
GROUP BY YourColumn
HAVING COUNT(*) > 1
ORDER BY COUNT(*) DESC

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Duplicate Delete Rows


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The table must have identity column, which will be used to identify the duplicate records. Table in example is has ID as Identity Column and Columns which have duplicate data are DuplicateColumn1, DuplicateColumn2 and DuplicateColumn3.


DELETE
FROM MyTable
WHERE ID NOT IN
(
SELECT MAX(ID)
FROM MyTable
GROUP BY DuplicateColumn1, DuplicateColumn2, DuplicateColumn2)


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Query to Retrieve the Nth Maximum value

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How to get 1st, 2nd, 3rd, 4th, nth topmost salary from an Employee table

The following solution is for getting 6th highest salary from Employee table ,

SELECT TOP 1 salary
FROM (
SELECT DISTINCT TOP 6 salary
FROM employee
ORDER BY salary DESC) a
ORDER BY salary
You can change and use it for getting nth highest salary from Employee table as follows
SELECT TOP 1 salary
FROM (
SELECT DISTINCT TOP n salary
FROM employee
ORDER BY salary DESC) a
ORDER BY salary

where n > 1 (n is always greater than one)

Same example converted in SQL Server 2005 to work with Database AdventureWorks.

USE AdventureWorks;
GO
SELECT TOP 1 Rate
FROM (
SELECT DISTINCT TOP 4 Rate
FROM HumanResources.EmployeePayHistory
ORDER BY Rate DESC) A
ORDER BY Rate
GO


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SQL SERVER - Query to find number Rows, Columns, ByteSize for each table in the current database - Find Biggest Table in Database

USE
GO
CREATE TABLE #temp (
table_name sysname ,
row_count INT,
reserved_size VARCHAR(50),
data_size VARCHAR(50),
index_size VARCHAR(50),
unused_size VARCHAR(50))
SET NOCOUNT ON
INSERT #temp
EXEC sp_msforeachtable 'sp_spaceused "?"'
SELECT a.table_name,
a.row_count,
COUNT(*) AS col_count,
a.data_size
FROM #temp a
INNER JOIN information_schema.columns b
ON a.table_name collate database_default
= b.table_name collate database_default
GROUP BY a.table_name, a.row_count, a.data_size
ORDER BY CAST(REPLACE(a.data_size, 'KB', '') AS integer) DESC
DROP TABLE #temp

SQL SERVER - Shrinking Truncate Log File - Log Full

SQL SERVER - Shrinking Truncate Log File - Log Full

December 30, 2006 by pinaldave

Sometime, it looks impossible to shrink the Truncated Log file. Following code always shrinks the Truncated Log File to minimum size possible.

USE DatabaseName
GO
DBCC SHRINKFILE(, 1)
BACKUP LOG WITH TRUNCATE_ONLY
DBCC SHRINKFILE(, 1)
GO

SQL SERVER - Delete Duplicate Records - Rows

Following code is useful to delete duplicate records. The table must have identity column, which will be used to identify the duplicate records. Table in example is has ID as Identity Column and Columns which have duplicate data are DuplicateValueColumn1, DuplicateValueColumn2 and DuplicateValueColumn3.

DELETE
FROM MyTable
WHERE ID NOT IN
(
SELECT MAX(ID)
FROM MyTable
GROUP BY DuplicatevalueColumn1, DuplicateValueColumn2,
DuplicateValueColumn2)



EXAMPLE
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if there is no key in the table then what ?

I have on table named [Duplicate] {ID int,FNAME varchar(10),MNAME varchar(10)}

Here there is no key and here are duplicate rows. so hoca can i delete this duplicate rows.

Check Data

ID FNAME LNAME
1 AAA CCC
2 BBB DDD
1 AAA CCC
2 BBB DDD
1 AAA CCC
2 BBB DDD
3 BCB DGD

Remove duplicate rows and keep the data in to the table like this using single query.

ID FNAME LNAME
1 AAA CCC
2 BBB DDD
3 BCB DGD