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SQL Quiz

Check what you have learned. All questions use the students and courses tables from this tutorial.

How the Quiz Works

Choose an answer for each question. The explanation tells you why it is right. If you miss one, go back to that lesson and try the examples again.

id	name	city	age	marks	course_id
1	Ali Khan	Karachi	19	78	1
2	Ayesha Siddiqui	Lahore	21	85	2
3	Bilal Ahmed	Karachi	22	64	1
4	Fatima Noor	Islamabad	20	92	3
5	Hamza Raza	Karachi	18	70	NULL
6	Sana Iqbal	Lahore	23	88	2

Question 1

Exercise

Which keyword reads data from a table?

SELECTGETREADOPEN

Question 2

Exercise

How many rows does this return? SELECT name FROM students WHERE city = 'Karachi';

2361

Question 3

Exercise

Which query shows the highest marks first?

SELECT name FROM students ORDER BY marks;SELECT name FROM students ORDER BY marks DESC;SELECT name FROM students SORT BY marks DESC;SELECT name FROM students ORDER marks HIGH;

Question 4

Exercise

What does SELECT AVG(marks) FROM students; return?

4779279.56

Question 5

Exercise

Which statement changes Ali Khan's marks to 80?

UPDATE students SET marks = 80;UPDATE students SET marks = 80 WHERE id = 1;CHANGE students marks = 80 WHERE id = 1;INSERT INTO students (marks) VALUES (80);

Question 6

Exercise

Which condition matches ages 19, 20 and 21?

age IN 19 TO 21age BETWEEN 19 AND 21age LIKE '19%21'age > 19 AND age < 21

Question 7

Exercise

An INNER JOIN between students and courses on students.course_id = courses.id returns how many rows?

6457

Question 8

Exercise

Which clause filters groups after GROUP BY?

WHEREHAVINGLIMITFILTER BY

Question 9

Exercise

Which statement removes the whole students table, including its structure?

DELETE FROM students;TRUNCATE TABLE students;DROP TABLE students;REMOVE students;

Question 10

Exercise

Which constraint makes a column both unique and not null, so it can identify each row?

FOREIGN KEYCHECKDEFAULTPRIMARY KEY

What Next?

Well done on finishing the SQL tutorial. Now practise on a real database: continue with the MySQL tutorial or the PostgreSQL tutorial.

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