Complex Queries workshop

Intermediate SQL Workshop

  • Run psql
  • You may need to run CREATE DATABASE intermediate_sql;
  • To exit this shell, you can run CTRL d

Create tables

Let’s create some tables in the database.

CREATE TABLE students(id SERIAL, name TEXT);
CREATE TABLE classes(id SERIAL, name TEXT, teacher_id INT);
CREATE TABLE teachers(id SERIAL, name TEXT, room_number INT);
CREATE TABLE enrollments(id SERIAL, student_id INT, class_id INT, grade INT);

Add data

Let’s insert some students.

INSERT INTO students (name)
VALUES ('Penelope'),
       ('Peter'),
       ('Pepe'),
       ('Parth'),
       ('Priscilla'),
       ('Pablo'),
       ('Puja'),
       ('Patricia'),
       ('Piper'),
       ('Paula'),
       ('Pamela'),
       ('Paige'),
       ('Peggy'),
       ('Pedro'),
       ('Phoebe'),
       ('Pajak'),
       ('Parker'),
       ('Priyal'),
       ('Paxton'),
       ('Patrick');

Let’s add some teachers.

INSERT INTO teachers (name, room_number)
VALUES ('Phillips', 456),
       ('Vandergrift', 120),
       ('Mauch', 101),
       ('Patel', 320),
       ('Marquez', 560),
       ('Boykin', 200),
       ('Phlop', 333),
       ('Pendergrass', 222),
       ('Palomo', 323),
       ('Altshuler', 543),
       ('Aleman', 187),
       ('Ashley', 432),
       ('Bonacci', 399),
       ('Brazukas', 287),
       ('Brockington', 299),
       ('Brizuela', 376),
       ('Burkhart', 199),
       ('Choi', 463),
       ('Shah', 354),
       ('Dimaggio', 251);

Let’s add some classes.

INSERT INTO classes (name, teacher_id)
VALUES ('Cooking Pasta', 1),
       ('Yoga', 1),
       ('How to Guitar', 2),
       ('Gym', 3),
       ('Football', 4),
       ('Calculus', 5),
       ('Fruit', 6),
       ('Social Studies', 7),
       ('English', 8),
       ('Programming', 9),
       ('Singing', 10),
       ('Fashion', 11);

Lastly, let’s add some enrollments!

INSERT INTO enrollments (student_id, class_id, grade)
VALUES (1, 1, 60),
       (2, 2, 70),
       (2, 4, 100),
       (3, 2, 74),
       (4, 3, 82),
       (5, 3, 45),
       (5, 4, 50),
       (7, 11, 62),
       (7, 10, 76),
       (7, 9, 81),
       (7, 8, 91),
       (8, 8, 84),
       (9, 8, 88),
       (9, 7, 83),
       (10, 7, 93),
       (10, 5, 95),
       (11, 5, 95),
       (11, 11, 80),
       (11, 6, 95),
       (11, 1, 94),
       (11, 2, 60),
       (12, 6, 55),
       (13, 7, 97),
       (14, 10, 86),
       (15, 9, 77),
       (15, 4, 93),
       (15, 1, 73),
       (16, 2, 79),
       (16, 6, 73),
       (17, 7, 86),
       (17, 8, 91),
       (17, 9, 93),
       (18, 10, 94),
       (19, 4, 84),
       (20, 1, 85),
       (20, 11, 89),
       (20, 3, 98);

Practice!!

  • List all the students and their classes
  • List all the students and their classes and rename the columns to “student” and “class”
  • List all the students and their average grade
  • List all the students and a count of how many classes they are currently enrolled in
  • List all the students and their class count IF they are in more than 2 classes
  • List all the teachers for each student
  • List all the teachers for each student grouped by each student
  • Find the average grade for a each class
  • List students’ name and their grade IF their grade is lower than the average.