check the column which having all null values

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We have a table named "TEST" with 4 columns (Col1, Col2, Col3, Col4,.........,coln) with following data -

1, Test, Exam, Online ...........
NULL, NULL, NULL, NULL
2, NULL, Practice, NULL
NULL, NULL, NULL, NULL
NULL, NULL, NULL, NULL
NULL, NULL, NULL, NULL

How can i check the column which having all null values?
Thank you for all reply,
but i don't know how many number of columns are there.

Posted 20-Feb-13 19:26pm

Ganesh Thadishetti(HANAMKONDA)

Updated 18-Mar-13 3:00am

v3

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MalwareTrojan 21-Feb-13 4:12am

dint got your question. . . .

2 solutions

Solution 3

For unknow number o columns, try this:

SQL

USE DataBaseName;

DECLARE @cols NVARCHAR(2000)
DECLARE @tblName NVARCHAR(30)
DECLARE @sql NVARCHAR(MAX)

SET @tblName = 'TableName'
SET @cols = STUFF((SELECT DISTINCT '],[' + syscolumns.name 
					FROM sysobjects INNER JOIN syscolumns  ON sysobjects.id = syscolumns.id  
					WHERE (sysobjects.xtype = 'u' and sysobjects.name = @tblName)
					--ORDER BY '],[' + syscolumns.colid 
			FOR XML PATH('')),1,2,'') + ']'

SELECT @cols AS [columns]


SET @sql = 'SELECT ' + @cols + ' ' +
		'FROM ' + @tblName + ' ' +
		'WHERE COALESCE(' + @cols + ') IS NULL'
EXEC (@sql)

RISK: Length of string reserved for column names - stored in @cols variable - can exceed declared value (2000)!

Posted 5-Apr-13 2:35am

Maciej Los

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gvprabu · Accepted Answer · 2013-02-20T20:18:00

Hi ,

Use COALESCE() Function like as follows

SQL

CREATE TABLE #Test (Col1 INT, Col2 INT, Col3 INT, Col4 INT)

INSERT INTO #Test(Col1,Col2,COl3, Col4) VALUES(NULL,1,NULL,NULL),(NULL,NULL,NULL,NULL)
INSERT INTO #Test(Col1,Col2,COl3, Col4) VALUES(NULL,NULL,2,NULL),(NULL,NULL,NULL,NULL)
INSERT INTO #Test(Col1,Col2,COl3, Col4) VALUES(NULL,NULL,NULL,3),(NULL,NULL,NULL,NULL)

SELECT Col1,Col2,Col3, Col4 FROM #Test WHERE COALESCE(Col1, Col2, Col3, Col4) IS NULL

Regards,
GVPrabu