Codecademy - Aggregate Functions

'downloads' 하면 안됨

그룹화 해줘야함

avg함수 없이 그냥 downloads라고만 하면 각 그룹의 첫번 째 값으로 반환됨

We can’t use WHERE here because we don’t want to filter the rows; we want to filter groups

 

• COUNT(): count the number of rows
• SUM(): the sum of the values in a column
• MAX()/MIN(): the largest/smallest value
• AVG(): the average of the values in a column
• ROUND(): round the values in the column

Aggregate functions combine multiple rows together to form a single value of more meaningful information.

• GROUP BY is a clause used with aggregate functions to combine data from one or more columns.
• HAVING limit the results of a query based on an aggregate property.