ITPEC IP April 2024 Question 28
ITPEC IP April 2024 — Question 28 of 100
Projection extracts columns, selection extracts rows, and join combines related tables. Therefore operation I is projection, II is selection, and III is join.
Projection chooses specified attributes such as customer name and city from every applicable tuple. Selection applies a condition and keeps only records satisfying it, such as customers in Seoul. A join matches rows from two or more relations by related columns, such as a foreign key and primary key, to form a combined result.
Answer (c)
Why not others:
- (a) incorrectly assigns join to column extraction and selection to table combination
- (b) correctly starts with projection but swaps selection and join
- (d) swaps projection and selection
Key rule: Projection is vertical column choice, selection is horizontal row filtering, and join connects data across relations.
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