In order for this book to be useful, you need access to a PostgreSQL client that is allowed to execute queries on a server. Ideally, you'll also be the server administrator. Full client and server packages for PostgreSQL are available for most popular operating systems at http://www.postgresql.org/download/. All the examples here are executed at the Command Prompt, usually running the PSQL program. This makes them applicable to most platforms. It's straightforward to do most of these operations by using a GUI tool for PostgreSQL, such as pgAdmin or OmniDB:

• pgAdmin: https://www.pgadmin.org/download/
• OmniDB: https://omnidb.org/en/downloads-en

We also provide a PDF file that has color images of the screenshots/diagrams used in this book. You can download it here: http://www.packtpub.com/sites/default/files/downloads/9781789537581_ColorImages.pdf.

There are a number of text conventions used throughout this book.

CodeInText: Indicates code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles. Here is an example: "Copy the data files (excluding the pg_wal directory)."

A block of code is set as follows:

CREATE USER repuser
      SUPERUSER
       LOGIN
       CONNECTION LIMIT 1
       ENCRYPTED PASSWORD 'changeme';

When we wish to draw your attention to a particular part of a code block, the relevant lines or items are set in bold:

SELECT *FROM mytable
 WHERE  (col1, col2, … ,colN) IN
 (SELECT col1, col2, … ,colN
  FROM mytable
  GROUP BY col1, col2, … ,colN
  HAVING count(*) > 1);

Any command-line input or output is written as follows:

$ postgres --single -D /full/path/to/datadir postgres

Bold: Indicates a new term, an important word, or words that you see onscreen. For example, words in menus or dialog boxes appear in the text like this. Here is an example: "Select System info from the Administration panel."