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Learning PostgreSQL 10

Learning PostgreSQL 10 - Second Edition

By : Juba, Volkov
2.3 (6)
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Learning PostgreSQL 10

Learning PostgreSQL 10

2.3 (6)
By: Juba, Volkov

Overview of this book

PostgreSQL is one of the most popular open source databases in the world, supporting the most advanced features included in SQL standards. This book will familiarize you with the latest features released in PostgreSQL 10. We’ll start with a thorough introduction to PostgreSQL and the new features introduced in PostgreSQL 10. We’ll cover the Data Definition Language (DDL) with an emphasis on PostgreSQL, and the common DDL commands supported by ANSI SQL. You’ll learn to create tables, define integrity constraints, build indexes, and set up views and other schema objects. Moving on, we’ll cover the concepts of Data Manipulation Language (DML) and PostgreSQL server-side programming capabilities using PL/pgSQL. We’ll also explore the NoSQL capabilities of PostgreSQL and connect to your PostgreSQL database to manipulate data objects. By the end of this book, you’ll have a thorough understanding of the basics of PostgreSQL 10 and will have the necessary skills to build efficient database solutions.
Table of Contents (17 chapters)
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Common mistakes in writing queries


There are some common mistakes and bad practices that a developer may fall into, which are as follows:

Unnecessary operations

There are different ways to introduce extra operations such as hard disk scans, sorting, and filtering. For example, some developers often use DISTINCT even if it is not required, or do not know the difference between UNION, UNION ALL, EXCEPT, EXCEPT ALL, and so on. This causes slow queries, especially if the expected number of rows is high. The following two queries are equivalent simply because the table has a primary key, but the one with DISTINCT is much slower:

postgres=# \timing 
Timing is on.
postgres=# SELECT * FROM guru;
Time: 85,089 ms
postgres=# SELECT DISTINCT * FROM guru;
Time: 191,335 ms

Another common mistake is to use DISTINCT with UNION, as in the following query:

postgres=# SELECT * FROM guru UNION SELECT * FROM guru;
Time: 267,258 ms
postgres=# SELECT DISTINCT * FROM guru UNION SELECT DISTINCT * FROM guru;
Time: 346...
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Learning PostgreSQL 10
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