Is there a way to select the column names of a certain table except those columns with only null values without knowing how many columns the table have.
-------------------------
| col1 | col2 | col3 |
------------------------
| val1 | null | val2 |
| val1 | null | null |
| null | null | val2 |
-------------------------
Should result in:
------------------------------------
| cols_except_those_with_null_only |
-----------------------------------
| col1 |
| col3 |
------------------------------------
Thanks!
Create a stored procedure with following content:
create table #cols (colname varchar(255), nullCount int)
insert into #cols (colname)
select name from syscolumns where id = object_id('tblTest')
declare @c varchar(255)
declare curCols cursor for select colname from #cols
open curCols
fetch next from curCols into @c
while @@fetch_status = 0 begin
exec ('update #cols set nullCount = (select count(*) from tblTest where ' + @c + ' is not null) where colname = ''' + @c + '''')
fetch next from curCols into @c
end
close curCols
deallocate curCols
declare @rv table (cols_expect_those_with_null_only varchar(255))
insert into @rv (cols_expect_those_with_null_only)
select colname from #cols
where nullCount > 0
drop table #cols
select * from @rv
Try this, it's not the tidiest but will work, just set @Table
to your table name.
DECLARE @Table AS VARCHAR(100)
SET @Table = 'Example'
DECLARE @TempColumn VARCHAR(100)
DECLARE @Sql NVARCHAR(300)
DECLARE @HasNoNulls INT
CREATE TABLE #Columns (
ColumnName VARCHAR(100)
)
DECLARE ColumnCursor CURSOR FOR
SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.Columns
WHERE TABLE_NAME = @Table
OPEN ColumnCursor
FETCH NEXT FROM ColumnCursor
INTO @TempColumn
WHILE @@FETCH_STATUS = 0
BEGIN
SET @SQL = 'SELECT @HasNoNullsOut = COUNT(*) FROM ' + @Table + ' WHERE ' + @TempColumn + ' IS NOT NULL'
PRINT @SQL
EXECUTE sp_executesql @SQL, N'@HasNoNullsOut int OUTPUT', @HasNoNullsOut=@HasNoNulls OUTPUT
IF @HasNoNulls > 0
BEGIN
INSERT INTO #Columns
VALUES(@TempColumn)
END
FETCH NEXT FROM ColumnCursor
INTO @TempColumn
END
CLOSE ColumnCursor
DEALLOCATE ColumnCursor
SELECT * FROM #Columns
DROP TABLE #Columns
With this structure you can do a query in a store procedure that allows you to ask for each column name of the table and if it has null values without caring how many columns your table has
SELECT a.[name] as 'Table',
b.[name] as 'Column'
FROM sysobjects a
INNER JOIN syscolumns b
ON a.[id] = b.[id]
where table='yourtable'
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