Page 105 - SQL

Name GreatHouseAllegience

Arya Stark

Cercei Lannister

Myrcella Lannister

Yara Greyjoy

Catelyn Stark

Sansa Stark

Without GROUP BY, COUNT will simply return a total number of rows:

SELECT Count(*) Number_of_Westerosians
FROM Westerosians

returns...

Number_of_Westerosians

6

But by adding GROUP BY, we can COUNT the users for each value in a given column, to return
the number of people in a given Great House, say:

SELECT GreatHouseAllegience House, Count(*) Number_of_Westerosians
FROM Westerosians
GROUP BY GreatHouseAllegience

returns...

House Number_of_Westerosians

Stark 3

Greyjoy 1

Lannister 2

It's common to combine GROUP BY with ORDER BY to sort results by largest or smallest
category:

SELECT GreatHouseAllegience House, Count(*) Number_of_Westerosians
FROM Westerosians
GROUP BY GreatHouseAllegience
ORDER BY Number_of_Westerosians Desc

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