When bytes null and when bytes null

1. zookeeper null
If the column in the table is allowed to be empty, it cannot be used to determine whether to wait for the value to be null. On the contrary, the where clause must be used to determine whether the column or partition number is null. The SQL statement of the lower limit returns the rows in which the lastname column is equal to the value of the parameter number @ lastname, or the lastname column and parameter number @ lastname are empty.

Select * From MERs where (lastname = @ Lastname) or (lastname is null and @ lastname is null ))

2. Maximum bytes null values
When sending a null value as a numeric value, you must use dbnull. value instead of null. For example:

1 Sqlparameter Param =   New Sqlparameter ( " @ Name " , Sqldbtype. nvarchar, 20 );
2 Param. Value = Dbnull. value;