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:

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.