Simulate a conditional unique rule
SQL
Hard
6 views
Problem Description
In Seats(bus_id, seat_no, status), seat_no should be unique per bus only for active seats (status='ACTIVE'). Write a SQL approach that enforces it using a separate table ActiveSeats and FK/PK.
Output Format
DDL statement(s)
Sample Test Case
Input:
Seats(bus_id, seat_no, status)
Constraints
Use a helper table to enforce partial uniqueness
Official Solution
CREATE TABLE ActiveSeats (bus_id INT NOT NULL, seat_no INT NOT NULL, PRIMARY KEY (bus_id, seat_no));
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