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Learning PostgreSQL 10

You're reading from   Learning PostgreSQL 10 A beginner's guide to building high-performance PostgreSQL database solutions

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Product type Paperback
Published in Dec 2017
Publisher
ISBN-13 9781788392013
Length 488 pages
Edition 2nd Edition
Languages
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Authors (2):
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Andrey Volkov Andrey Volkov
Author Profile Icon Andrey Volkov
Andrey Volkov
Salahaldin Juba Salahaldin Juba
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Salahaldin Juba
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Toc

Table of Contents (17) Chapters Close

Preface 1. Relational Databases FREE CHAPTER 2. PostgreSQL in Action 3. PostgreSQL Basic Building Blocks 4. PostgreSQL Advanced Building Blocks 5. SQL Language 6. Advanced Query Writing 7. Server-Side Programming with PL/pgSQL 8. OLAP and Data Warehousing 9. Beyond Conventional Data Types 10. Transactions and Concurrency Control 11. PostgreSQL Security 12. The PostgreSQL Catalog 13. Optimizing Database Performance 14. Testing 15. Using PostgreSQL in Python Applications 16. Scalability

Function predefined variables


The PL/pgSQL functions have several special variables that are created automatically in the top-level block. For example, if the function returns a trigger, then several variables, such as NEW, OLD, and TG_OP, are created.

In addition to the trigger special values, there is a Boolean variable called FOUND. This is often used in combination with DML and PERFORM statements to conduct sanity checks. The value of the FOUND variable is affected by the SELECT, INSERT, UPDATE, DELETE, and PERFORM statements. These statements set FOUND to true if at least one row is selected, inserted, updated, or deleted.

The PERFORM statement is similar to the SELECT statement, but it discards the result of the query. Finally, the EXECUTE statement does not change the value of the FOUND variable. The following examples show how the FOUND variable is affected by the INSERT and PERFORM statements:

DO $$
BEGIN
  CREATE TABLE t1(f1 int);

  INSERT INTO t1 VALUES (1);
  RAISE NOTICE '%',...
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