Complete HW Advanced-SQL
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Advanced-SQL/hw5.sql
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217
Advanced-SQL/hw5.sql
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--
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-- Name: Nicholas Tamassia
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--
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-- Write your queries below each comment. Please use good style (one clause
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-- per line, JOIN syntax, indentation) and make sure all queries end with a
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-- semicolon. When necessary, limit the output to the first 200 results.
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--
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-- DO NOT MODIFY OR DELETE ANY OTHER LINES!
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--
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-- -----------------------------------------------------------------------------
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-- Connect to air database
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\c air
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-- -----------------------------------------------------------------------------
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--
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\echo
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\echo Query #1
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--
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-- List all last names in the database that start with the letter M. Use the
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-- lower() function to convert all last names to lowercase. Show how many times
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-- each last name is used. Note: last names are in more than one table.
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--
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-- Schema: count, last_name
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-- Order: count (descending), last_name
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SELECT COUNT(*) AS count, last_name
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FROM (
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SELECT lower(last_name) AS last_name FROM passenger
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UNION ALL
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SELECT lower(last_name) FROM account
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UNION ALL
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SELECT lower(last_name) FROM frequent_flyer
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)
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WHERE last_name LIKE 'm%'
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GROUP BY last_name
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ORDER BY count DESC, last_name
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LIMIT 200;
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--
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\echo
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\echo Query #2
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--
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-- Show the passengers who have flown out of Dulles (IAD) but have never flown
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-- out of Orlando (MCO).
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--
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-- Schema: passenger_id, first_name, last_name
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-- Order: passenger_id
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SELECT passenger_id, first_name, last_name
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FROM (
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SELECT passenger_id, first_name, last_name
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FROM passenger
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JOIN booking ON passenger.booking_id = booking.booking_id
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JOIN booking_leg ON booking.booking_id = booking_leg.booking_id
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JOIN flight ON booking_leg.flight_id = flight.flight_id
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WHERE departure_airport = 'IAD'
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EXCEPT
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SELECT passenger_id, first_name, last_name
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FROM passenger
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JOIN booking ON passenger.booking_id = booking.booking_id
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JOIN booking_leg ON booking.booking_id = booking_leg.booking_id
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JOIN flight ON booking_leg.flight_id = flight.flight_id
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WHERE departure_airport = 'MCO'
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)
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ORDER BY passenger_id
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LIMIT 200;
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--
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\echo
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\echo Query #3
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--
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-- Find the passengers who have not been issued a boarding pass, but whose
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-- booked itinerary includes a domestic flight from Dhaka (depart airport
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-- DAC, arrive in Bangladesh BD).
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--
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-- Schema: first_name, last_name, iso_country
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-- Order: passenger_id
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SELECT p.first_name, p.last_name, a.iso_country
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FROM passenger AS p
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JOIN booking AS b ON p.booking_id = b.booking_id
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JOIN booking_leg AS bl ON b.booking_id = bl.booking_id
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JOIN flight AS f ON bl.flight_id = f.flight_id
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JOIN airport AS a ON f.arrival_airport = a.airport_code
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WHERE f.departure_airport = 'DAC'
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AND a.iso_country = 'BD'
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AND NOT EXISTS (
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SELECT 1
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FROM boarding_pass
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WHERE boarding_pass.passenger_id = p.passenger_id
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)
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ORDER BY p.passenger_id
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LIMIT 200;
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--
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\echo
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\echo Query #4
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--
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-- For each airport, find the percentage of flights that have departed over 10
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-- minutes late. Note that in order to avoid integer division, you must cast at
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-- least one of the values to a float. For example: CAST(late_flights AS float)
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-- Also, you will need to use the interval data type to represent 10 minutes.
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--
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-- Schema: departure_airport, percentage (calculated value)
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-- Order: departure_airport
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SELECT
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f.departure_airport,
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100.0 * CAST(SUM(
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CASE WHEN actual_departure > scheduled_departure + INTERVAL '10 minutes'
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THEN 1 ELSE 0 END
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) AS float)
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/
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COUNT(*) AS percentage
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FROM flight f
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GROUP BY f.departure_airport
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ORDER BY f.departure_airport
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LIMIT 200;
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-- -----------------------------------------------------------------------------
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-- Connect to jmudb database
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\c jmudb
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-- -----------------------------------------------------------------------------
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--
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\echo
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\echo Query #5
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--
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-- For each subject, how many sections in Fall 2024 were taught with more than
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-- 15 students enrolled? Be careful not to count the same section twice!
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--
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-- Schema: subject, count
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-- Order: count (descending), subject
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SELECT subject,
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COUNT(DISTINCT nbr) AS count
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FROM enrollment
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WHERE term = 1248
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AND enrolled > 15
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GROUP BY subject
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ORDER BY count DESC, subject
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LIMIT 200;
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--
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\echo
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\echo Query #6
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--
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-- For each instructor, count the total number of students they taught in CS
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-- courses over the past three academic years (Summer 2022 to Spring 2025).
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--
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-- Schema: instructor, students (calculated value)
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-- Order: students (descending), instructor
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SELECT instructor, SUM(students.enrolled) AS students
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FROM (
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SELECT DISTINCT instructor, term, nbr, enrolled
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FROM enrollment
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WHERE subject = 'CS'
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AND term BETWEEN 1225 AND 1251
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) as students
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GROUP BY instructor
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ORDER BY students DESC, instructor
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LIMIT 200;
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--
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\echo
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\echo Query #7
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-- List all sections in Fall 2024 with more that 100 students enrolled, and
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-- rank them by course (i.e., the section with the most students is rank #1).
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--
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-- Schema: subject, number, nbr, enrolled, rank
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-- Order: subject, number, nbr
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SELECT
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subject,
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number,
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nbr,
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enrolled,
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RANK() OVER (
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PARTITION BY subject, number
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ORDER BY enrolled DESC
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) AS rank
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FROM (
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SELECT subject, number, nbr, enrolled
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FROM enrollment
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WHERE term = 1248 AND enrolled > 100
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GROUP BY subject, number, nbr, enrolled
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)
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ORDER BY subject, number, nbr
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LIMIT 200;
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--
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\echo
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\echo Query #8
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-- Rank departments in Spring 2025 by their total enrollment, i.e., who has the
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-- most students enrolled across all sections. (Hint: two nested subqueries)
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--
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-- Schema: subject, total, rank
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-- Order: subject
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SELECT t1.subject,
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t1.total,
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RANK() OVER (ORDER BY t1.total DESC) AS rank
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FROM (
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SELECT subject, SUM(enrolled) as total
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FROM (
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SELECT DISTINCT subject, term, nbr, enrolled
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FROM enrollment
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WHERE term = 1251
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)
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GROUP BY subject
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) AS t1
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ORDER BY subject
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LIMIT 200;
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