SQL · Beginner

SQL & Databases

Fifty-six lessons on SELECT through JOIN, GROUP BY, transactions, indexes, security and the real reports an academy runs every month.

56 steps, written for someone starting from zero: the lessons plus a checkpoint quiz task after every ten. Each lesson opens with a starting point you have to change, not the finished answer. Work through it in order and you finish with a program you wrote yourself — the kind of thing you can show in an interview, not a certificate you bought.

56 tasks 6 sections 0 done

Start task 1

Section 1 · Reading data

1 What a database is SQL —
2 SELECT the basics SQL —
3 Choose columns SQL —
4 WHERE filters rows SQL —
5 Numbers in WHERE SQL —
6 AND, OR, NOT SQL —
7 ORDER BY sorts SQL —
8 Sort by two columns SQL —
9 LIMIT and OFFSET SQL —
10 COUNT rows SQL —

Section 2 · Summaries

11 SUM a column SQL —
12 AVG, MIN, MAX SQL —
13 ROUND the answer SQL —
14 GROUP BY SQL —
15 HAVING SQL —
16 Count distinct SQL —
17 Aliases SQL —
18 CASE WHEN SQL —
19 NULL and COALESCE SQL —
20 INNER JOIN SQL —

Section 3 · Joins and subqueries

21 JOIN three tables SQL —
22 LEFT JOIN keeps everyone SQL —
23 Find students who never paid SQL —
24 JOIN with a condition SQL —
25 Aggregate over a join SQL —
26 UNION SQL —
27 Subquery in WHERE SQL —
28 Subquery in FROM SQL —
29 String functions SQL —
30 LIKE pattern search SQL —

Section 4 · Changing data

31 Dates as text SQL —
32 INSERT a row SQL —
33 INSERT several rows SQL —
34 UPDATE one row SQL —
35 UPDATE with a calculation SQL —
36 DELETE a row SQL —
37 Transactions SQL —
38 CREATE TABLE SQL —
39 Primary keys SQL —
40 Foreign keys SQL —

Section 5 · Real academy queries

41 Views SQL —
42 Indexes SQL —
43 Monthly revenue SQL —
44 Collected vs expected SQL —
45 Students per course SQL —
46 Top paying student SQL —
47 Pagination query SQL —
48 Duplicate check SQL —
49 Safe UPDATE checklist SQL —
50 SQL injection SQL —

Capstone: reports a client would pay for

51 Keep the newest rows SQL —
52 Find groups above a threshold SQL —
53 Join students to their course SQL —
54 Filter with a subquery SQL —
55 Label rows with CASE SQL —
56 Count rows safely with LEFT JOIN SQL —

Final exam and certificate

Twenty questions from the whole track. Pass mark is 60%. Retakes are free and the best score is the one printed on your certificate.

Create a free account to take the exam