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() |