> 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/sql/dml-commands/test-for-empty-relations.md).

# Test for Empty Relations

The **exists** construct returns the value true if the argument subquery is nonempty.

* exists r ⇔ r ≠ Ø
* not exists r ⇔ r = Ø