CODEWITHSUNDEEP
sqlsql-serversql-server-2008t-sql
Jill Clover
Jill Clover

Reputation: 2328

SQL: Select columns WITHOUT NULL values only in a table

This question is the exact opposite of SQL: Select columns with NULL values only.

Given a table with 1024 columns, how to find all columns WITHOUT null values?

Input:a table with 1024 columns

Output:col1_name(no null values) col2_name(no null values)...

Upvotes: 3

Views: 10351

Answers (2)

pmbAustin
pmbAustin

Reputation: 3980

If you want to avoid using a CURSOR, this method will simply list out the column names of any columns that have no NULL values in them anywhere in the table... just set the @TableName at the top:

DECLARE @tableName sysname;
DECLARE @sql nvarchar(max);
SET @sql = N'';
SET @tableName = N'Reports_table';

SELECT @sql += 'SELECT CASE WHEN EXISTS (SELECT 1 FROM ' + @tableName + ' WHERE '+ COLUMN_NAME + ' IS NULL) THEN NULL ELSE ''' + COLUMN_NAME +
''' END AS ColumnsWithNoNulls UNION ALL '
FROM INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = @tableName
SELECT @sql = SUBSTRING(@sql, 0, LEN(@sql) - 10);
IF OBJECT_ID('tempdb..#Results') IS NOT NULL DROP TABLE #Results;
CREATE TABLE #Results (ColumnsWithNoNulls sysname NULL);
INSERT INTO #Results EXEC(@sql);
SELECT * FROM #Results WHERE ColumnsWithNoNulls IS NOT NULL

As a bonus, the results are in a temp table, #Results, so you can query to get any information you want... counts, etc.

Upvotes: 4

Kostya
Kostya

Reputation: 1605

i modified the Select columns with NULL values only.

to work for your case :

SET ANSI_WARNINGS OFF 

declare @col varchar(255), @cmd varchar(max)

DECLARE getinfo cursor for
SELECT c.name FROM sys.tables t JOIN sys.columns c ON t.Object_ID = c.Object_ID
WHERE t.Name = 'Reports_table'

OPEN getinfo

FETCH NEXT FROM getinfo into @col

WHILE @@FETCH_STATUS = 0
BEGIN
    SELECT @cmd = 'IF (SELECT sum(iif([' + @col + '] is null,1,null)) FROM Reports_table) is null  BEGIN print ''' + @col + ''' end'
    exec(@cmd)

    FETCH NEXT FROM getinfo into @col
END

CLOSE getinfo
DEALLOCATE getinfo

SET ANSI_WARNINGS on

Upvotes: 0

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