Database Engine Operations
DB engine = "relational algebra virtual machine":
| selection (σ) |
| projection (π) |
| join (⋈) |
| union (∪) |
| intersection (∩) |
| difference (-) |
| sort |
| group |
| aggregate |
For each of these operations:
- various data structures and algorithms are available
- DBMSs may provide only one, or may provide a choice
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