Like most network-capable database systems, PostgreSQL fits into a client-server paradigm. The heart of PostgreSQL is the server backend, or the postmaster process. It is called a “backend” because it is not meant to directly interface with a user; rather, it can be connected to with a variety of clients.
When you start the PostgreSQL service, the postmaster process starts running in the background, listening to a specific TCP/IP port for connections from clients. Unless explicitly configured, postmaster will bind to, and listen on, port 5432.
There are several interfaces available through which clients may connect to the postmaster process. The examples in this book use psql, the most portable and readily accessible client distributed with PostgreSQL.
This chapter covers psql basics, how to create and use tables, and how to retrieve and manage data within those tables. It also addresses SQL sub-queries and views.