SELECT, PROJECT, and RENAME are ____________relational operations.

Question

BlackTom AI · Accepted Answer

Consider the set of relational algebra operations in question. 
Option 1: 'unary' — This fits because SELECT (σ), PROJECT (π), and RENAME (ρ) each take a single relation as input and produce a new relation as output, making them unary operations. 
Option 2: 'binary' — A binary operation would require two input relations (for example, union or set difference). Since these three operate on one relation at a time, labeling them binary would be incorrect. 
Option 3: 'ternary' — A ternary operation would involve three input relations, which is not the case here; these operators do not combine multiple relations in one step. 
Option 4: 'domain' — This term does not describe the arity of an operation; it references the set of permissible values or attributes, not how many relations an operation consumes. 
Option 5: 'None of the above' — Since there is a valid option among the list, this statement would be inaccurate. 
In summary, the practical characterization of SELECT, PROJECT, and RENAME is that they operate on a single relation, i.e., they are unary operations, whereas the other options do not accurately describe their arity or have unrelated meanings.

SELECT, PROJECT, and RENAME are ____________relational operations.

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