Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Programming
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Databases
Mail Systems
openSolaris
Eclipse Documentation
Techotopia.com
Virtuatopia.com

How To Guides
Virtualization
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Windows
Problem Solutions
Privacy Policy

  




 

 

Databases - Practical PostgreSQL
Previous Page Home Next Page

Token Formatting Considerations

As described in the preceding section, each sequential element of a SQL statement is considered a token. What may not be immediately clear, however, is that tokens may be kept all on the same line, or they may be split across several lines, as extra whitespace is ignored by PostgreSQL's parser.

Consider the SQL statement in Example 3-1, which is executed first on a single line, and then executed again, split across two separate lines. Both SELECT statements instruct the database to display the entire contents of the my_list table:

Example 3-1. Spaces and newlines

testdb=# 
SELECT * FROM my_list;

                     todos
------------------------------------------------
 Pick up laundry.
 Send out bills.
 Wrap up Grand Unifying Theory for publication.
(3 rows)

testdb=# 
SELECT *

testdb-# 
       FROM

testdb-# 
       my_list;

                     todos
------------------------------------------------
 Pick up laundry.
 Send out bills.
 Wrap up Grand Unifying Theory for publication.
(3 rows)

In Example 3-1 there are several newlines and spaces between the second statement's tokens. As you can see by the identical output, PostgreSQL ignores the extra newlines and spaces, making both statements semantically equivalent. You can take advantage of this behavior by splitting a long string of tokens across numerous lines for improved readability of your SQL statement. This probably isn't necessary for statements as simple as those in Example 3-1, but it can be quite helpful when dealing with complex SQL statements with numerous clauses, expressions, and conditions. Throughout this book we will periodically split some statements over several lines to help show what each part of the statement is intended to accomplish.

Databases - Practical PostgreSQL
Previous Page Home Next Page

 
 
  Published under the terms of the Open Publication License Design by Interspire