> For the complete documentation index, see [llms.txt](https://vikram-bajaj.gitbook.io/cs-gy-6083-principles-of-database-systems/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://vikram-bajaj.gitbook.io/cs-gy-6083-principles-of-database-systems/main-1/sql/dml-commands/nested-subqueries.md).

# Nested Subqueries

A subquery is a select-from-where query that is nested within another query.

A common use of subqueries is to perform tests for set membership (in/not in), set comparisons and set cardinality.

Ex. to get the names of instructors who get a salary greater than that of at least one instructor in the Biology department:

```
select name from instructor where salary > some (select salary from instructor where dept_name='Biology')
```

Ex. to get the names of instructors who get a salary greater than that of all the instructors in the Biology department:

```
select name from instructor where salary > all (select salary from instructor where dept_name='Biology')
```