## Chapter 39. Triggers

**Table of Contents**

[39.1. Overview of Trigger Behavior](trigger-definition.html)

[39.2. Visibility of Data Changes](trigger-datachanges.html)

[39.3. Writing Trigger Functions in C](trigger-interface.html)

[39.4. A Complete Trigger Example](trigger-example.html)

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 This chapter provides general information about writing trigger functions. Trigger functions can be written in most of the available procedural languages, including PL/pgSQL ([Chapter 43](plpgsql.html)), PL/Tcl ([Chapter 44](pltcl.html)), PL/Perl ([Chapter 45](plperl.html)), and PL/Python ([Chapter 46](plpython.html)). After reading this chapter, you should consult the chapter for your favorite procedural language to find out the language-specific details of writing a trigger in it.

 It is also possible to write a trigger function in C, although most people find it easier to use one of the procedural languages. It is not currently possible to write a trigger function in the plain SQL function language.

