Fundamentals

Literals

A literal is just a fixed value, written directly into a query, not a reference to anything else.

SELECT 'Dune';    -- character literal
SELECT 42;        -- integer literal
SELECT 3.14;       -- real literal
SELECT title FROM movies;   -- title, movies: no quotes, schema objects

• Words or characters are character literals, wrapped in single or double quotes, 'Dune' or "Dune".
• No quotes at all means it's not a literal, it's a reference to a schema object, a table name or column name, like title or movies above.
• Numbers are numeric literals, split into two kinds: integer literals (whole numbers, 42) and real literals (numbers with a decimal point, 3.14).