Argument Behavior | C/C++ UDMs | Teradata Vantage - Argument Behavior - Advanced SQL Engine - Teradata Database

Truncation of Character String Arguments

The session transaction mode affects character string truncation.

The normal truncation rules apply to a result string. For more information, see Teradata Vantage™ - Data Types and Literals, B035-1143.

Behavior When Using NULL as a Literal Argument

The RETURNS NULL ON NULL INPUT and CALLED ON NULL INPUT options in the METHOD specification of the CREATE TYPE statement determine what happens if the NULL keyword is used as any of the input arguments.

If the METHOD specification in the CREATE TYPE statement does not specify either RETURNS NULL ON NULL INPUT or CALLED ON NULL INPUT, the default is CALLED ON NULL INPUT.

NULL as a literal argument is compatible with a parameter of any data type. For example, consider the following address UDT and map_it method:

CREATE TYPE address
   AS ( street VARCHAR(20),
        zip CHAR(5) )
   NOT FINAL
   INSTANCE METHOD map_it( CHAR(4), INTEGER )
   RETURNS INTEGER
   SPECIFIC mapit
   LANGUAGE C
   PARAMETER STYLE SQL
   DETERMINISTIC
   NO SQL;

CREATE METHOD map_it( map_type CHAR(4), code INTEGER )
RETURNS INTEGER
FOR address
EXTERNAL NAME 'CS!map_it!udm_src/map_it.c!F!mapit';

You can successfully use the NULL keyword as any method argument:

CREATE TABLE locations( id INTEGER, details address );

SELECT details.map_it('4415', NULL) FROM locations;
SELECT details.map_it(NULL, NULL) FROM locations;

Passing the NULL keyword as an argument to overloaded methods can result in errors unless Vantage can identify which method to invoke without ambiguity. For details, see Calling a Function That is Overloaded.

Overflow and Numeric Arguments

To avoid numeric overflow conditions, the C/C++ function should define a decimal data type as big as it can handle.

If the assignment of the value of an input or output numeric argument would result in a loss of significant digits, a numeric overflow error is reported.

For example, consider a instance method that takes a DECIMAL(2,0) argument:

CREATE TYPE circle
   AS ( x INTEGER,
        y INTEGER,
        radius INTEGER )
   NOT FINAL
   INSTANCE METHOD smldec( DECIMAL(2,0) )
   RETURNS INTEGER
   SPECIFIC smldec
   LANGUAGE C
   PARAMETER STYLE SQL
   DETERMINISTIC
   NO SQL;

CREATE METHOD smldec( DECIMAL(2,0) )
RETURNS INTEGER
FOR circle
EXTERNAL NAME 'CS!smldec!udm_src/smldec.c!F!smldec';

Passing a number with a maximum of two digits is successful:

SELECT circle_column.smldec(99) FROM circle_tbl WHERE c_id = 100;

An attempt to pass a number larger than 99 or smaller than -99 would result in a loss of significant digits.

SELECT circle_column.smldec(100) FROM circle_tbl WHERE c_id = 100;
   
 Failure 2616 Numeric overflow occurred during computation.

Any fractional numeric data that is passed or returned that does not fit as it is being assigned is rounded according to Teradata rounding rules. For more information on rounding, see Teradata Vantage™ - Data Types and Literals, B035-1143.