How to insert null in datetime type column in sql server

Question

I have a table in which there are some datetime type columns. I use a stored procedure to insert values into the table. In the stored procedure I have variables that accept null

Answer 1

First of all, to be able to insert null into a database column, the column must accept nulls. Open the table in the designer, and see if the relevant column is nullable or not. If it's not and you try to insert a null value, you'll get the error:

Cannot insert the value NULL into column 'InsertDate', table 'TableName'; column does not allow nulls.

That said, since you are using stored procedures to insert data, I would recommend using default values for the parameters on the procedure level, instead of burdening the aplication code. Than, you can just not set the parameter on the application side, and it would work correctly:

 create procedure InsertIntoTable
   -- ....other parameters here...
   @InsertDate datetime = null -- this means that if the value is not supplied, 
                               -- null is used by default
 as begin
   insert into TableName (InsertDate) values (@InsertDate)
 end

and on the C# side, just do:

if (!string.IsNullOrWhitespace(InsertDate.Text)) {
  // check to see if the entered text is actually a date
  DateTime insertDate = ... some parsing/verification code...;
  cmd1.Parameters["@InsertDate"].Value = insertDate;
}

Note that there is no else branch, so if the InsertDate is empty, the parameter is not sent at all.