Зміст курсу

SQL Tutorial for Beginners

1. Database & Introduction to Syntax

Meet the SQL Select the Songs!SQL Select Column SQL Distinct SQL Where Challenge Where SQL And, Or, Not

2. SQL Aggregate Functions

SQL Min and Max Challenge Min and Max SQL Count, Sum, Avg Challenge Count

3. Filtering Statements

SQL Null SQL Like Challenge Like SQL Between SQL Order By Challenge Order By SQL Group By Challenge Group By SQL Top and Limit SQL Aliases SQL Having Challenge Having SQL Comments

SQL Count, Sum, Avg

Similar to the previous chapter, SUM, AVG, and COUNT functions are aggregate functions that return the sum of field, average value, and count. SUM and AVG can be applied only for numbers, and COUNT - for fields of any data type.


              1
            
SELECT AVG(price) FROM songs

If you want to find the number of records with some condition, you can apply COUNT to the *.

This query outputs the number of records with the release date in the 20th century:


              12
            
SELECT COUNT(*) FROM songs
WHERE year <= 2000

Aggregate functions and Distinct

If you want to apply aggregate function to the unique values, write DISTINCT inside this function and before the column name:


              1
            
SELECT COUNT(DISTINCT song) FROM songs

Завдання

Now you have to write a query that helps you to calculate the total number of singers. Remember that some singers have two or more records in the table, but you have to pick these singers only once.

Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантів

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 2. Розділ 3

SQL Count, Sum, Avg


              1
            
SELECT AVG(price) FROM songs

If you want to find the number of records with some condition, you can apply COUNT to the *.

This query outputs the number of records with the release date in the 20th century:


              12
            
SELECT COUNT(*) FROM songs
WHERE year <= 2000

Aggregate functions and Distinct

If you want to apply aggregate function to the unique values, write DISTINCT inside this function and before the column name:


              1
            
SELECT COUNT(DISTINCT song) FROM songs

Завдання

Now you have to write a query that helps you to calculate the total number of singers. Remember that some singers have two or more records in the table, but you have to pick these singers only once.

Все було зрозуміло?

Дякуємо за ваш відгук!

Секція 2. Розділ 3

SQL Count, Sum, Avg


              1
            
SELECT AVG(price) FROM songs

If you want to find the number of records with some condition, you can apply COUNT to the *.

This query outputs the number of records with the release date in the 20th century:


              12
            
SELECT COUNT(*) FROM songs
WHERE year <= 2000

Aggregate functions and Distinct

If you want to apply aggregate function to the unique values, write DISTINCT inside this function and before the column name:


              1
            
SELECT COUNT(DISTINCT song) FROM songs

Завдання

Now you have to write a query that helps you to calculate the total number of singers. Remember that some singers have two or more records in the table, but you have to pick these singers only once.

Все було зрозуміло?

Дякуємо за ваш відгук!


              1
            
SELECT AVG(price) FROM songs

If you want to find the number of records with some condition, you can apply COUNT to the *.

This query outputs the number of records with the release date in the 20th century:


              12
            
SELECT COUNT(*) FROM songs
WHERE year <= 2000

Aggregate functions and Distinct

If you want to apply aggregate function to the unique values, write DISTINCT inside this function and before the column name:


              1
            
SELECT COUNT(DISTINCT song) FROM songs

Завдання

Now you have to write a query that helps you to calculate the total number of singers. Remember that some singers have two or more records in the table, but you have to pick these singers only once.

Секція 2. Розділ 3