The structure of PL/pgSQL is fairly simple, mainly due to the fact that each portion of code is designed to exist as a
function. While it may not look immediately similar to other languages, PL/pgSQL's structure is similar to other programming
languages such as C, in which each portion of code acts (and is created) as a function, all variables must be declared before
being used, and code segments accept arguments when called and return arguments at their end.
Regarding its syntax, PL/pgSQL functions are case insensitive. You can use mixed, upper-, or lowercase for keywords and
identifiers. Additionally, you will notice the use of pairs of apostrophes (single quotes) in many places within this
chapter. These are required whenever a single apostrophe would ordinarily be used. The pair of apostrophes is a means to
escape an apostrophe within the function definition to PostgreSQL, since a function definition is actually a large string
constant within a CREATE FUNCTION statement.
This section will discuss the block organization of PL/pgSQL code, how to use comments, how PL/pgSQL expressions are
organized, and the usage of statements.