> 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/the-relational-model-details/relational-query-languages/relative-expressive-power.md).

# Relative Expressive Power

* Safe TRC and DRC are as powerful as (basic) relational algebra
* Extended relational algebra is
  * more powerful than TRC/DRC
  * useful for defining SQL semantics
  * useful for designing SQL queries
  * useful for understanding SQL execution
* Relational calculus is
  * useful for designing SQL queries