Finding NULL column names in SQL Server - sql-server

Question

In SQL Server, is there any quick way to find out null column names for a particular record other than using CASE expression?
For eg:
I have one record whose values are like:
id|FName|LName|Dept
1 |NULL |Smith|NULL
Expected result is: FName, Dept
So, every time I will have only one record and I need to find the list of NULL columns for it.

Answer 1

if it's just a result set then you can't do it in sql-server.
but you can use other language making a query tool to do it like below C# code :
void Main(){
var nullColumnsName = GetNullColumnsName("select 1 id,null FName,'Smith' LName ,null Dept");
Console.WriteLine(nullColumnsName); //result : FName,Dept
}
IEnumerable<string> GetNullColumnsName(string sql)
{
using (var cnn = Connection)
{
if(cnn.State == ConnectionState.Closed) cnn.Open();
using(var cmd = cnn.CreateCommand()){
cmd.CommandText = sql;
using(var reader = cmd.ExecuteReader(CommandBehavior.SequentialAccess|CommandBehavior.SingleResult|CommandBehavior.SingleRow))
{
if(reader.Read())
{
for (int i = 0; i < reader.FieldCount; i++)
{
var value = reader.GetValue(i);
if(value is DBNull)
yield return reader.GetName(i);
}
}
while (reader.Read()) {};
}
}
}
}

Answer 2

As per your this statement: "every time I will have only one record and I need to find the list of NULL columns for it"
You can store these values like follows:
Column | Values
FName | Null
LName | Smith
Dept | Null
and I assume that id is the primary key so as per your requirement if you want to store that then you can or if not, it's your choice.
SELECT Column FROM table
WHERE Values IS NULL;

Answer 3

You can use the following script. The script:
opens a cursor over all columns in the table definition
then, for each column, it queries all values in the column
if there is no non-null value in the column, it prints the name of the column
create table tmpTable (id int, FName varchar(32), LName varchar(32), Dept varchar(32))
insert into tmpTable values(1, null, 'Smith', null)
go
declare #column varchar(128)
declare #sql varchar(max)
declare c cursor for
select c.name from sys.tables t join sys.columns c on t.object_id = c.object_id
where t.name = 'tmpTable'
open c
fetch next from c into #column
while ##fetch_status = 0
begin
select #sql = 'if not exists (select * from tmpTable where ' + #column + ' is not null) begin print + ''' + #column + ''' end'
exec(#sql)
fetch next from c into #column
end
close c
deallocate c
go
drop table tmpTable
For your test case, this is the output of the script:
FName
Dept
Note: This script will work regardless how many rows you have in the table.
Edit:
I had written my answer before the following clarification was added "It is a result set". My solution works with a table (as I am querying the system catalogs) and will not cover the clarified scenario (using a result set).