Database management systems notes
Relational Algebra
The six operators every SQL query is secretly built from. Every section is a drawn page beside a clear written explanation, about 20 minutes in all.
- Chapter 6 of 34
- About 20 minutes
- 8 sections
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In this chapter
- Why an algebra at all
- Selection: choosing rows
- Projection: choosing columns
- Union, difference and intersection
- Cartesian product: every pairing
- Rename: making self-comparison possible
- Joins, built from what came before
- Division, and composing a real query
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