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SQL & Databases

Querying data: SELECT, filters, JOIN, aggregates

What you'll build
📘A solid foundation
⚡Practice in the browser
🎯Mini-projects
🎓Course certificate
📘 32 lessons⏱ 1-2 evenings🎓 Intermediate
🎯 Mission
Master SQL & Databases
⚡+370XP
🏆CertificatePDF
🎓Course complete
Progress0 / 32 · 0%
Next up: What is SQL

Course program

01

Основы SELECT

0 / 6 lessons
⌄
  1. 01

    What is SQL

    Tables and rows•SELECT•The first query⚡ +10
    ▶ Now
  2. 02

    Column list and AS

    Column list•AS — alias•Column order⚡ +10
    Open
  3. 03

    DISTINCT — unique values

    DISTINCT•Remove duplicates•Several columns⚡ +10
    Open
  4. 04

    ORDER BY — sorting

    ASC and DESC•Several columns•Sort order⚡ +10
    🔒 Pro
  5. 05

    LIMIT — limiting rows

    LIMIT N•TOP-N query•OFFSET⚡ +10
    🔒 Pro
  6. 06

    Calculations in SELECT

    Arithmetic•Computed columns•The AS alias⚡ +10
    🔒 Pro
02

Фильтрация: WHERE

0 / 4 lessons
⌄
  1. 07

    WHERE: comparison operators

    =, <>, <, >•>=, <=•Filtering rows⚡ +10
    🔒 Pro
  2. 08

    AND, OR, NOT — compound conditions

    AND — both•OR — at least one•NOT — negation⚡ +10
    🔒 Pro
  3. 09

    IN, BETWEEN, LIKE

    IN list•BETWEEN range•LIKE pattern⚡ +10
    🔒 Pro
  4. 10

    IS NULL — empty values

    What NULL is•IS NULL / IS NOT NULL•NULL pitfalls⚡ +10
    🔒 Pro
03

Агрегаты и группировка

0 / 5 lessons
⌄
  1. 11

    COUNT — counting rows

    COUNT(*)•COUNT(column)•NULL is ignored⚡ +10
    🔒 Pro
  2. 12

    SUM, AVG, MIN, MAX

    Sum and average•Minimum / maximum•Aggregate AS⚡ +10
    🔒 Pro
  3. 13

    GROUP BY — grouping

    GROUP BY column•COUNT per group•SUM per group⚡ +10
    🔒 Pro
  4. 14

    HAVING — filtering groups

    HAVING vs WHERE•A condition on an aggregate•Group filter⚡ +10
    🔒 Pro
  5. 15

    GROUP BY + ORDER BY + LIMIT

    Grouping + sorting•TOP-N groups•A full query⚡ +10
    🔒 Pro
04

JOIN: объединение таблиц

0 / 5 lessons
⌄
  1. 16

    INNER JOIN — joining tables

    What a JOIN is•The ON condition•INNER JOIN⚡ +10
    🔒 Pro
  2. 17

    LEFT JOIN — keep all rows

    LEFT JOIN•NULL when no match•INNER vs LEFT⚡ +10
    🔒 Pro
  3. 18

    Multiple JOINs

    Two JOINs in a row•Three tables•Aliases⚡ +10
    🔒 Pro
  4. 19

    JOIN + GROUP BY

    JOIN + grouping•A customer’s purchases•SUM + JOIN⚡ +10
    🔒 Pro
  5. 20

    JOIN + HAVING + small groups

    HAVING COUNT•Number of orders•Active customers⚡ +10
    🔒 Pro
05

DML и схема

0 / 5 lessons
⌄
  1. 21

    INSERT — adding a row

    INSERT INTO•VALUES list•Column list⚡ +10
    🔒 Pro
  2. 22

    UPDATE — updating data

    UPDATE SET•The WHERE condition•Several columns⚡ +10
    🔒 Pro
  3. 23

    DELETE — removing rows

    DELETE FROM•The WHERE condition•Delete everything⚡ +10
    🔒 Pro
  4. 24

    CREATE TABLE — creating a table

    CREATE TABLE•Data types•PRIMARY KEY⚡ +10
    🔒 Pro
  5. 25

    Subqueries

    Subquery•SELECT inside WHERE•Scalar result⚡ +10
    🔒 Pro
06

Аналитика мини-проекты

0 / 7 lessons
⌄
  1. 26

    Project: top sellers

    JOIN + SUM•TOP products•A full query⚡ +10
    🔒 Pro
  2. 27

    Project: customer activity

    LEFT JOIN + COUNT•Customers without orders•The CASE expression⚡ +10
    🔒 Pro
  3. 28

    Project: price categories

    CASE price category•Price ranges•GROUP BY category⚡ +10
    🔒 Pro
  4. 29

    Project: above-average cities

    Subquery + AVG•WHERE vs HAVING•Sorting the result⚡ +10
    🔒 Pro
  5. 30

    Project: store report — revenue

    Complex JOIN + SUM•Revenue per customer•Ranking⚡ +10
    🔒 Pro
  6. 31

    Project: country analysis

    GROUP BY country•COUNT + SUM + AVG•Full analysis⚡ +10
    🔒 Pro
  7. 32

    Final project: store dashboard

    Everything together•JOIN + AGG + HAVING•A full report
    Course complete
    🔒 Pro