SQL NULL value

The SQL NULL value represents a null or empty value in a database column. The NULL value is distinct from all valid values for a given data type.

For example, the INTEGER data type holds a four-byte integer. This four-byte data type can hold 232 (or 4,294,967,296) values:
  • zero
  • positive values: 1 to 2,147,483,647
  • negative values: -1 to -2,147,483,647
  • NULL value: 2,147,483,648 (the maximum negative number)
Because the representation of the NULL value is unique to each data type, the DataBlade® API provides the following functions to assist in determining whether a value is the SQL NULL value.
Handling the SQL NULL value DataBlade® API function
Can a column hold NULL values?

(Was the NOT NULL constraint used to defined the column?)

mi_column_nullable(), mi_parameter_nullable()
Does the value represent a NULL value? mi_fp_argisnull(), mi_fp_setargisnull(), mi_fp_returnisnull(), mi_fp_setreturnisnull()
Does the UDR handle NULL arguments?

(Has the UDR been registered to indicate that it contains code to handle NULL values as arguments?)

mi_func_handlesnulls()
Does an expensive-UDR argument hold a NULL value? mi_funcarg_isnull()