Getting Started with DB2 Express-C

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242 Getting Started with DB2 Express-C procedures with more complex logic, we recommend you use IBM Data Studio which includes a debugger. 14.2.2 User-defined functions A user-defined function (UDF) is a database application object that allows users to extend the SQL language with their own logic. A function always returns a value or values normally as a result of the business logic included in the function. To invoke a function, use it within a SQL statement, or with the values function. In DB2 you can develop UDFs in several languages including SQL PL, Java, C/C++, OLE, CLR. This simple example shows how to create and call a SQL PL UDF from the DB2 Command Window or Linux shell: db2 create function F1() returns integer begin return 1000; end db2 values F1 In the example, function F1 is a function returning an integer value of 1000. The VALUES statement can be used to invoke the function. Like in the case of stored procedures, we recommend you create functions using IBM Data Studio. 14.2.3 Triggers A trigger is an object that automatically performs an operation on a table or view. A triggering action on the object where the trigger is defined causes the trigger to be fired. A trigger is normally not considered an application object; therefore, database developers normally don't code triggers, but database administrators do. Because some coding is required, we have included triggers in this section. Below is an example of a trigger: create trigger myvalidate no cascade before insert on T1 referencing NEW as N for each row begin atomic set (N.myxmlcol) = XMLVALIDATE(N.myxmlcol according to xmlschema id myxmlschema); end In this example, the trigger is fired before an INSERT operation on table T1. The trigger will insert the value (which is an XML document), but will invoke the XMLVALIDATE function to validate this XML document with a given schema. Chapter 15, DB2 pureXML talks more about XML and XML schemas.
14.3 Client-side development Chapter 14 - Introduction to DB2 Application Development 243 As the name suggests, in client-side development, the application developers code their programs on a client and then connect and access the DB2 database using the application program interfaces (APIs) that are provided with DB2. In this section we discuss: • Embedded SQL • Static SQL vs Dynamic SQL • CLI and ODBC • JDBC, SQLJ and pureQuery • OLE DB • ADO.NET • PHP • Ruby on Rails • Perl • Python 14.3.1 Embedded SQL Embedded SQL applications are applications where SQL is embedded into a host language such as C, C++, or COBOL. The embedded SQL application can include static or dynamic SQL as described in the next section. Figure 14.2 shows how an embedded SQL application is built. Figure 14.2 - Building embedded SQL applications
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GETTING STARTED WITH DB2 Express-C
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Contents About this book ..........
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Contents 7 6.3 DB2 storage model ..
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Contents 9 13.4.2 Cursor stability
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About this book Notices and tradema
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About this Book 13 A book for the c
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About this Book 15 Foreword Innovat
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1 Chapter 1 - What is DB2 Express-C
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Chapter 1 - What is DB2 Express-C?
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1.8 Moving up to another DB2 editio
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8 Chapter 8 - Working with Database
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