In this chapter we continue to discuss SQL, this time with a practical focus. We'll address creating tables, populating
tables with data, and managing that data via SQL statements.
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.
The
psql
client is a command-line client distributed with PostgreSQL. It is often called the
interactive monitor
or
interactive terminal
. With
psql
, you
get a simple yet powerful tool with which you can directly interface with the PostgreSQL server, and thereby begin
exploring SQL.
