18.1 subqueries in where clause - mergen-sergio/DBest GitHub Wiki

This section presents examples of subqueries inside the WHERE clause, one of the most common patterns in SQL. Subqueries in this context can take various forms, often incorporating additional SQL keywords such as IN, EXISTS, ALL, and ANY. These keywords influence how the subquery interacts with the main query, leading to different filtering behaviors.

Beyond these standard constructs, subqueries in the WHERE clause can also appear in boolean expressions and direct comparisons, further expanding their versatility in query design. The following examples illustrate these different possibilities.