pl/sql: how to write an apostrophe?

Self-tutoring about pl/sql: the tutor mentions a way to enter a single quote.

With pl/sql, strings are enclosed in single quotes. So how can one write an apostrophe?

A solution seems to be to write two apostrophes: ‘It”s working!’, for instance. In my experience, that means two separate apostrophes rather than double quotes.

Source:

techonthenet.com