What is the difference between HAVING and WHERE in SQL?

What is the difference between HAVING and WHERE in an SQL SELECT statement?

EDIT: I have marked Steven’s answer as the correct one as it contained the key bit of information on the link:

When GROUP BY is not used, HAVING behaves like a WHERE clause

The situation I had seen the WHERE in did not have GROUP BY and is where my confusion started. Of course, until you know this you can’t specify it in the question.

Answer

HAVING specifies a search condition for a group or an aggregate function used in SELECT statement.

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