CS 4320 SQL Fun. With Justin Miron

Transcription

1 CS 4320 SQL Fun With Justin Miron

2 The Scenario Students(snum INTEGER, sname NVARCHAR(50), major NVARCHAR(50), level NVARCHAR(50), age INTEGER) Class(class_id INTEGER, cname NVARCHAR(50), meets_at TIME, room NVARCHAR(50)) Enrolled(snum INTEGER, class_name STRING) Faculty(faculty_id INTEGER, name NARCHAR(50), dept_id INTEGER) What are the FOREIGN and PRIMARY keys?

3 Warm up - Together! Question 1: 1:M Find the name of all Juniors (level = JR who are enrolled in a class taught by Barack Obama

4 Finding Obama s Juniors 1. Find all classes taught by Barack Obama SELECT * FROM Class C, Faculty F WHERE F.faculty_id = C.faculty_id AND F.name = Barack Obama Find the name of all Juniors (level = JR who are enrolled in a class taught by Barack Obama 2. Find all Juniors enrolled in a specific class SELECT * FROM Students S, Enrolled E WHERE S.snum = C.snum AND E.cname = CS4320 AND S.level = JR

5 Putting it all together 1. Find all classes taught by Barack Obama SELECT * FROM Class C, Faculty F WHERE F.faculty_id = C.faculty_id AND F.name = Barack Obama 2. Find all Juniors enrolled in a specific class SELECT * FROM Students S, Enrolled E WHERE S.snum = C.snum AND E.cname = CS4320 AND S.level = JR Find the name of all Juniors (level = JR who are enrolled in a class taught by Barack Obama SOLUTION: SELECT S.sname FROM Class C, Faculty F, Students S, Enrolled E WHERE F.faculty_id = C.faculty_id AND F.name = Barack Obama AND S.snum = E.snum AND E.cname = C.cname AND S.level = JR

6 The Question after the first Question 2 Hint 1: MAX aggregate Hint 2: Nested Query Find the age of the oldest student who is either a CS major or enrolled in a class taught by Justin Miron

7 The Answer Find the age of the oldest student who is either a CS major or enrolled in a class taught by Justin Miron SELECT MAX(s.age) FROM Student S WHERE (S.major = CS ) OR S.num IN (SELECT E.snum FROM Class C, Enrolled E, Faculty F WHERE E.cname = C.name AND C.faculty_id = F.faculty_id AND F.fname = Justin Miron ) All the students enrolled in a class taught by Justin Miron

8 The last question before we change it up a bit Question 3 Hint 1: GROUP Hint 2: BY For each student level EXCEPT JR, return the average age of students at that level in (level, average age) pairs.

9 The Answer SELECT S.level, AVG (S.age) FROM Student S WHERE S.level!= JR GROUP BY S.level For each student level EXCEPT JR, return the average age of students at that level in (level, average age) pairs. sname level age Rory FR 19 level age Jess SO 19 Lorelai SO 35 Luke SE 40 FR 19 SO 27 SE Paris SE 19 Logan SE 20

10 Scenario Number Zoo Animals(animal_id INTEGER, name NVARCHAR(50), species NVARCHAR(50), danger INTEGER, age INTEGER, enclosure_id INTEGER) Enclosure(enclosure_id INTEGER, name NVARCHAR(50), niceness INTEGER, vlog_id INTEGER) VisitorLog(vlog_id INTEGER, name NVARCHAR(50), happiness INTEGER)

11 Scenario Number Zoo

12 Breaking the question down For each species, find the ratio of average enclosure niceness to average danger. - Ratio - Math - For each species - Probably a GROUP BY - Average - Aggregates

13 What is the SQL Query For each species, find the ratio of average enclosure niceness to average danger. SELECT A.species, AVG(E.niceness)/AVG(A.danger) FROM Animals A, Enclosure E WHERE A.enclosure_id = E.enclosure_id GROUP BY A.species

14 Break this question down Find the maximum happiness of any visitor for each enclosure with an animal older than 12 - Three table join (Animals - happiness, Enclosure - vlog_id, VisitorLog vlog_id) - WHERE Animals.age > 12 - Aggregate - MAX(VisitorLog.happiness) - GROUP BY enclosure_id

15 What is the SQL Query Find the maximum happiness of any visitor for each enclosure with an animal older than 12 SELECT E.enclosure_id, MAX(V.happiness) FROM Animals A, Enclosure E, VisitorLog V WHERE V.vlog_id = E.vlog_id AND A.enclosure_id = E.enclosure_id GROUP BY E.enclosure_id HAVING ANY(A.age) > 12

16 Scenario Number Zoo Question N What is the hardest single SQL query question you can come up with?

17 Scenario Number Zoo Question N+1 What characterizes the query you came up with?

18 Scenario Number Zoo Question N+2 Write the SQL query.