Relational Playground: Teaching the Duality of Relational Algebra and SQL

Students in introductory data management courses are often taught how to write queries in SQL. This is a useful and practical skill, but it gives limited insight into how queries are processed by relational database engines. In contrast, relational algebra is a commonly used internal representation of queries by database engines, but can be challenging for students to grasp. We developed a tool we call Relational Playground for database students to explore the connection between relational algebra and SQL.

Transcript

1. Michael Mior
   Relational Playground
   Teaching the Duality of Relational
   Algebra and SQL
   

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2. • Relational Algebra and SQL
   • Query Optimization
   • Demo
   • Future Work
   

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3. Context
   ▸ Introductory courses in databases
   (big data) for grads and undergrads
   ▸ Relational algebra is taught first,
   followed by SQL
   ▸ Students are expected to know how to
   convert between the two
   3
   

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4. Relational
   Algebra
   ▸ Gives a better intuition for how queries
   are executed by the database
   ▸ Important for understanding query
   optimization
   ▸ Enabling students to experiment
   provides an infinite source of examples
   4
   

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5. SQL
   ▸ Many students come with some
   knowledge of SQL
   ▸ Most students will likely be writing SQL
   ▸ Being able to connect this with
   relational algebra improves
   understanding of query execution
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6. Relational
   Playground
   ▸ Currently Relational Playground
   supports SELECT, JOIN, WHERE, and
   ORDER BY
   ▸ Relational Playground provides a single
   implementation for each operator
   ▸ All queries are executed completely in
   the browser (there is no backend)
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7. Query
   optimization
   Start with a “canonical” relational algebra
   representation:
   1. Join all tables in the query
   2. Apply any filtering
   3. Sort the results
   4. Project the final set of columns
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8. Future
   Work
   ▸ Additional operators and expanded
   query support
   ▸ More query optimizations
   ▸ Explainable query execution
   ▸ Detailed student evaluations
   8
   

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9. Demo
   relationalplayground.com
   

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13. Acknowledgements
    Carson
    Bloomingdale
    Aryan Jha
    

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14. Questions?
    relationalplayground.com
    

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