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SQL Tutorial for Beginners
SQL Tutorial for Beginners
SQL Group By
GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:
SELECT COUNT(Id), singer FROM songs GROUP BY singer
This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:
-- do not run this query SELECT col1, col2, ... FROM table WHERE condition GROUP BY col1, col2, ... ORDER BY col1, col2, ...;
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантівВсе було зрозуміло?
SQL Group By
GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:
SELECT COUNT(Id), singer FROM songs GROUP BY singer
This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:
-- do not run this query SELECT col1, col2, ... FROM table WHERE condition GROUP BY col1, col2, ... ORDER BY col1, col2, ...;
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантівВсе було зрозуміло?
SQL Group By
GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:
SELECT COUNT(Id), singer FROM songs GROUP BY singer
This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:
-- do not run this query SELECT col1, col2, ... FROM table WHERE condition GROUP BY col1, col2, ... ORDER BY col1, col2, ...;
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантівВсе було зрозуміло?
GROUP BY is an operator that puts rows with the same values of the field in groups. It creates one row for each group, so it makes sense to use some aggregate function in SELECT. For example, let's group our songs by singers, and find a number of songs for each singer:
SELECT COUNT(Id), singer FROM songs GROUP BY singer
This query will return a list of singers, as well as, for each of them, the number of songs. Each singer represents a unit or group, and COUNT() aggregate function is applied for records in the group. You can use GROUP BY with ORDER BY, and also group by multiple columns. Here is a syntax of query:
-- do not run this query SELECT col1, col2, ... FROM table WHERE condition GROUP BY col1, col2, ... ORDER BY col1, col2, ...;
Завдання
For each singer, create groups with info about singer and price of the most expensive song. Order these groups by singer.
Перейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантівПерейдіть на комп'ютер для реальної практикиПродовжуйте з того місця, де ви зупинились, використовуючи один з наведених нижче варіантів