fundamentals/database/notes/05-sql-primer-worksheet-answers.md

Queries

Insert queries

1. Insert a row with all columns

    INSERT INTO students
    VALUES (1, 'Tantia', 'Tope', 't@t.com', '1234567890', 1);

2. Insert a row with some columns

    INSERT INTO students (first_name, last_name)
    VALUES ('Tantia', 'Tope');

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Select Queries

1. Get all students

   SELECT *
   FROM students;
   

2. Get first and last name of all students

   SELECT first_name, last_name
   FROM students;
   

3. Get first name of all students with output column name as Student Name

   SELECT first_name AS "Student Name"
   FROM students;
   

4. Get all unique addresses of all students

   SELECT DISTINCT address FROM students;
   

5. Get all students with ID equal to 1

   SELECT * FROM students WHERE id = 1;
   

6. Get all students with IQ greater than 150

   SELECT * FROM students WHERE iq > 150;
   

7. Get all students with IQ less than 100

   SELECT * FROM students WHERE iq < 100;
   

8. Get all students with IQ greater than 100 and less than150

   SELECT * FROM students
   WHERE iq > 100 AND iq < 150;
   

9. Get all students with IQ greater than 100 or less than 150

   SELECT * FROM students
   WHERE iq BETWEEN 100 AND 150;
   

10. Get all students with first name Tantia

    SELECT * FROM students WHERE first_name = 'Tantia';
    

11. Get all students with first name Tantia and last name Tope

    SELECT * FROM students
    WHERE first_name = 'Tantia' AND last_name = 'Tope';
    

12. Get all students with first name John or first name Mycroft

    SELECT * FROM students
    WHERE first_name = 'John' OR first_name = 'Mycroft';
    

13. Get all students with name John Watson or Mycroft Holmes

    SELECT * FROM students
    WHERE (first_name = 'John' AND last_name = 'Watson')
    OR (first_name = 'Mycroft' AND last_name = 'Holmes');
    

14. Get all students without the first name John

    SELECT * FROM students WHERE first_name <> 'John';
    

15. Get all students without the first name John or last name Mycroft

    SELECT * FROM students
    WHERE first_name <> 'John' AND last_name <> 'Mycroft';
    

16. Get all students with first name starting with T

    SELECT * FROM students WHERE first_name LIKE 'T%';
    

17. Get all students with last name ending with walker

    SELECT * FROM students WHERE last_name LIKE '%walker';
    

18. Get all students with first name containing T

    SELECT * FROM students WHERE first_name LIKE '%T%';
    

19. Get all students with last name in the format ___walker

    SELECT * FROM students WHERE last_name LIKE '___walker';
    

20. Get all students in Jhansi and London

    SELECT * FROM students
    WHERE address IN ('Jhansi', 'London');
    

21. Get all students which do not have a batch id

    SELECT * FROM students WHERE batch_id IS NULL;
    

22. Get the first 5 students

    SELECT * FROM students LIMIT 5;
    

23. Get the first 5 students sorted by IQ

    SELECT * FROM students ORDER BY iq LIMIT 5;
    

24. Get the first 5 students sorted by IQ in descending order

    SELECT * FROM students ORDER BY iq DESC LIMIT 5;
    

25. Get the first 5 students sorted by IQ in descending order and then by first name

    SELECT * FROM students 
    ORDER BY iq DESC, first_name LIMIT 5;
    

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Update Queries

1. Update a row

   UPDATE students SET first_name = 'Tantia' WHERE id = 1;
   

2. Update a row with a condition

   UPDATE students SET first_name = 'Tantia' WHERE id = 1 AND first_name = 'John';
   

3. Update multiple columns

   UPDATE students SET first_name = 'Tantia', last_name = 'Tope' WHERE id = 1 AND first_name = 'John';
   

Delete Queries

1. Delete a row with a condition

   DELETE FROM students
   WHERE id = 1 AND first_name = 'John';
   

2. Delete a multiple rows

   DELETE FROM students WHERE id IN (1, 2, 3);
   

Joining Queries

1. Get first name and last name of all students and their batch names

   SELECT students.first_name, students.last_name, batches.name FROM students JOIN batches ON students.batch_id = batches.id;
   

2. Get first name and last name of all students and their instructor names

   SELECT s.first_name, s.last_name, i.first_name, b.name, i.last_name 
   FROM students s 
       JOIN batches b ON s.batch_id = b.id
       JOIN instructors i ON b.instructor_id = i.id;