About this book's code examples

The sample output shown here has been created with PostgreSQL's psql utility, usually running on a Linux system. Most of the code will work the same way if you are using a GUI utility like pgAdmin3 to access the server instead. When you see lines like this:

postgres=# SELECT 1;

The postgres=# part is the prompt shown by the psql command.

Examples in this book have been tested using PostgreSQL 9.2. They will probably work on PostgreSQL version 8.3 and later. There have not been many major changes to how server programming happens in the last few versions of PostgreSQL. The syntax has become stricter over time to reduce the possibility of mistakes in server programming code. Due to the nature of those changes, most code from newer versions will still run on the older ones, unless it uses very new features. However, the older code can easily fail to run due to one of the newly-enforced restrictions.

Switching to the expanded display

When using the psql utility to execute a query, PostgreSQL normally outputs the result using vertically aligned columns:

$ psql -c "SELECT 1 AS test"
 test 
------
    1
(1 row)

$ psql
psql (9.2.1)
Type "help" for help.

postgres=# SELECT 1 AS test;
 test 
------
    1
(1 row)

You can tell when you're seeing a regular output because it will end up showing the number of rows.

This type of output is hard to fit into the text of a book like this. It's easier to print the output from what the program calls the expanded display, which breaks each column into a separate line. You can switch to expanded using either the -x command-line switch, or by sending \x to the psql program. Here is an example of using each:

$ psql -x -c "SELECT 1 AS test"
-[ RECORD 1 ]
test | 1

$ psql
psql (9.2.1)
Type "help" for help.

postgres=# \x
Expanded display is on.
postgres=# SELECT 1 AS test;
-[ RECORD 1 ]
test | 1

Notice how the expanded output doesn't show the row count, and it numbers each output row. To save space, not all of the examples in the book will show the expanded output being turned on. You can normally tell which type you're seeing by differences like this, whether you're seeing rows or RECORD. The expanded mode will be normally preferred when the output of the query is too wide to fit into the available width of the book.