Duplicate a Column in SQL Server

Here’s a very simple but useful post that shows how to duplicate an existing column in SQL Server.

Assuming we have the following table structure with data:

CREATE TABLE #TmpTable(ColA varchar(10))
INSERT INTO #TmpTable SELECT 'ValueOne'
INSERT INTO #TmpTable SELECT 'ValueTwo'
INSERT INTO #TmpTable SELECT 'ValueThree'
INSERT INTO #TmpTable SELECT 'ValueFour'
INSERT INTO #TmpTable SELECT 'ValueFive'
INSERT INTO #TmpTable SELECT 'ValueSix'

Now to duplicate ColA, use the following code:

ALTER TABLE #TmpTable
ADD ColB varchar(10)
GO

UPDATE #TmpTable
SET ColB = ColA
GO

SELECT * FROM #TmpTable

As you can see, we have added a new column to the Table and used a simple Update statement to duplicate ColA. If the column already exists, you can avoid the ALTER TABLE.

OUTPUT