Generating test data

DBAs frequently need to generate test data for a variety of reasons, whether it’s for setting up a test database or just for generating a test case for a SQL performance issue.

How to do it...

To create a table of test data, we need the following:

• Some rows
• Some columns
• Some order

The steps are as follows:

1. First, generate a lot of rows of data. We use something named a set-returning function. You can write your own, although PostgreSQL includes a couple of very useful ones.
2. You can generate a sequence of rows using a query like the following:

   postgres=# SELECT * FROM generate_series(1,5);
   generate_series
   -----------------
                  1
                  2
                  3
                  4
                  5
   (5 rows)
   

3. Alternatively, you can generate a list of dates, like this:

   postgres=# SELECT date(t)
   FROM generate_series(now(), now() + '1 week', '1 day&apos...