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PostgreSQL Server Programming

You're reading from   PostgreSQL Server Programming Take your skills with PostgreSQL to a whole new level with this fascinating guide to server programming. A step by step approach with illuminating examples will educate you in the full range of possibilities.

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Product type Paperback
Published in Jun 2013
Publisher Packt
ISBN-13 9781849516983
Length 264 pages
Edition 1st Edition
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Toc

Table of Contents (17) Chapters Close

PostgreSQL Server Programming
Credits
About the Authors
About the Reviewer
www.PacktPub.com
Preface
1. What Is a PostgreSQL Server? 2. Server Programming Environment FREE CHAPTER 3. Your First PL/pgSQL Function 4. Returning Structured Data 5. PL/pgSQL Trigger Functions 6. Debugging PL/pgSQL 7. Using Unrestricted Languages 8. Writing Advanced Functions in C 9. Scaling Your Database with PL/Proxy 10. Publishing Your Code as PostgreSQL Extensions Index

Chapter 5. PL/pgSQL Trigger Functions

While it is generally a good practice to keep related code together and avoid "hidden" actions as part of main application code flows, there are also valid cases where it is a good practice to add some kind of general or cross-application functionality to the database using automated actions which happen each and every time a table is modified. That is, the actions are part of your data model and not your application code and you want to be sure that it is not possible to forget or bypass them in a similar way that constraints make it impossible to insert invalid data.

The tool for adding automated function calls to a table modifying event is called a trigger. Triggers are especially useful for cases where there are multiple different client applications—possibly from different sources and using different programming styles—accessing the same data using multiple different functions or straight SQL.

In PostgreSQL a trigger is defined in two steps:

  1. Define...

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