NexusDB

The support for user-defined procedures and functions, commonly known as stored procedures, makes NexusDB SQL a programmable database language, allowing users to automate tasks and extend the built-in functionality with custom routines.

NexusDB SQL supports user-defined procedures and functions written in SQL, called SQL routines, or hosted in a .NET assembly, called CLR routines (Enterprise Edition only). Since user-defined procedures and functions share many common characteristics and syntactic elements, they are both called SQL-invoked routines in standard SQL.

The procedure language in NexusDB adds power and flexibility to the functionality of user-defined procedures and functions written in SQL.

A user-defined procedure (UDP) can have both IN and OUT parameters. The OUT parameter is used to return a value from the procedure, and is equivalent to the result of a scalar-valued function. Procedures can also return a cursor by specifying a SELECT statement as the last statement in the routine body.

User-defined procedures are defined with the CREATE PROCEDURE statement and are invoked in SQL by the CALL statement.

The following example shows a procedure definition and how it is called in SQL:

       CREATE PROCEDURE addCourse (

// Parameter declarations with implicit IN mode

p_courseID SMALLINT,

p_courseName CHAR(20),

p_department CHAR(20),

p_numCredits TINYINT

       )

       MODIFIES SQL DATA -- We need write-access to update the courses table

       // We prefer to use a compound statement in the routine body, even with a single statement

       BEGIN

INSERT INTO courses

VALUES ( p_courseID, p_courseName, p_department, p_numCredits );

       END;

       CALL addCourse( :courseID, :courseName, :department, :numCredits );

Like functions in traditional programming languages, a user-defined function (UDF) always returns a value. The function result can be either a scalar value (scalar-valued function) or a table derived from a cursor specification (table-valued function), by specifying TABLE in the RETURNS clause of the function definition. A scalar-valued function can be referenced everywhere in SQL a scalar value is expected, while a table-valued function can be referenced in the FROM clause of a SELECT statement or invoked by calling the function as a separate SQL statement.

User-defined functions are defined with the CREATE FUNCTION statement and are invoked in SQL by the function name, see routine invocation.

The following example shows a function definition and how it is invoked in SQL:

       CREATE FUNCTION getFullName ( firstName VARCHAR(30), lastName VARCHAR(30) )

       RETURNS VARCHAR(61)

       /*

       LANGUAGE SQL is implicit

       NOT DETERMINISTIC is implicit

       CONTAINS SQL is implicit

       */

       RETURNS NULL ON NULL INPUT -- We don't invoke the function if any of the arguments are null

       // Multiple statements in the routine body must appear inside a compound statement

       BEGIN

DECLARE name VARCHAR(61);

SET name = firstName || ' ' || lastName;

RETURN name;

       END;

       UPDATE students

       SET studentName = getFullName( firstName, lastName )

       WHERE studentID = 211;

Procedure Language

SQL-Invoked Routines

SQL Procedure Statements