Relational algebra is a mathematical procedural query language containing operations to retrieve data. Relational calculus is its non-procedural, declarative counterpart.
Relational Algebra Operators
Basic Operators
Derived Operators
Relational Calculus Syntax Comparison
| Aspect | Tuple Relational Calculus (TRC) | Domain Relational Calculus (DRC) |
|---|---|---|
| Variables | Variables represent entire rows (tuples). e.g., t | Variables represent individual attributes (domains). e.g., x, y, z |
| Query focus | Filters rows. Very close to SQL concept. | Filters values in columns directly. More abstract. |
| Syntax | { t | P(t) } | { <x1, x2, ...> | P(x1, x2, ...) } |
| Example Query (Get Names of Students in CS dept) | { t.Name | t ∈ Students ∧ t.Dept = 'CS' } | { <n> | ∃ i, d (<i, n, d> ∈ Students ∧ d = 'CS') } |