SQL NULL Value

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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 (0)
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( )