feat: update structure

cs2102/labs/tutorials/tut04.sql

@@ -0,0 +1,65 @@
+-- How many loans involve an owner and a borrower from the same department?
+SELECT COUNT(*)
+FROM loan l,
+     student owner,
+     student borrower
+WHERE l.owner = owner.email
+AND l.borrower = borrower.email
+AND owner.department = borrower.department;
+
+-- For each faculty, print the number of loans that involve an owner and a borrower from this faculty?
+SELECT owner.department, COUNT(*)
+FROM loan l,
+     student owner,
+     student borrower
+WHERE l.owner = owner.email
+  AND l.borrower = borrower.email
+  AND owner.department = borrower.department
+GROUP BY owner.department;
+
+-- What are the average and the standard deviation of the duration of a loan? Round the results to the nearest integer.
+SELECT ROUND(AVG(l.returned - l.borrowed+1),0), ROUND(stddev_pop(l.returned - l.borrowed+1),0)
+FROM loan l;
+
+-- (a) Print the titles of the different books that have never been borrowed. Use a nested query.
+
+SELECT b.title
+FROM book b
+WHERE b.isbn13 NOT IN (
+    SELECT l.book
+    FROM loan l
+);
+
+-- (b) Print the name of the different students who own a copy of a book that they have never lent to anybody.
+SELECT s.name
+FROM student s
+WHERE s.email IN (
+    SELECT c.owner
+    FROM copy c
+    WHERE (c.owner, c.book,c.copy)NOT IN (
+        SELECT l.owner,l.book,l.copy
+        FROM loan l
+    ) );
+
+-- For each department, print the names of the students who lent the most.
+SELECT s.name,s.department, COUNT(*)
+FROM student s,loan l
+WHERE l.owner = s.email
+GROUP BY s.name, s.department
+HAVING COUNT(*) >= ALL
+(SELECT COUNT(*) FROM student s1, loan l1 WHERE l1.owner = s1.email AND s.department = s1.department GROUP BY s1.email);
+
+-- Print email and name of different students who borrowed all books authored by adam smith
+SELECT s.email, s.name
+FROM student s
+WHERE NOT EXISTS(
+    SELECT *
+    FROM book b
+    WHERE b.authors = 'Adam Smith'
+    AND NOT EXISTS(
+        SELECT *
+        FROM loan l
+        WHERE l.book = b.isbn13
+        AND l.borrower = s.email
+    )
+)