A major goal of this chapter was not only to show you how a variety of queries execute, but to demonstrate through many examples how to set up a query testing playground for exploring that yourself.
You shouldn't just read this chapter. You should load the dellstore2 data into your system and experiment with the queries yourself. It is possible that sometimes the results you get using the explain analyze statement are different; this may depend on the version of PostgreSQL you have, or on the indexes that have been created on the database, or it may depend on whether the system tables are updated (Analyze, Autoanalyze and Create Index are the processes that update the system tables ). For example if you are on PostgreSQL >= 9.2 and you have a table with an index in the field test_field and execute something such as SELECT field1 from table where test_field= 1...