Aggregate Functions
| MIN | returns the smallest value in a given column |
| MAX | returns the largest value in a given column |
| SUM | returns the sum of the numeric values in a given column |
| AVG | returns the average value of a given column |
| COUNT | returns the total number of values in a given column |
| COUNT(*) | returns the number of rows in a table |
Aggregate functions are used to compute against a "returned column of numeric data" from
your SELECT statement. They basically summarize the results of a particular column of
selected data. We are covering these here since they are required by the next topic, "GROUP BY". Although they are required for the "GROUP BY" clause, these functions can be used without the "GROUP BY" clause. For example:
SELECT AVG(salary)
FROM employee;
This statement will return a single result which contains the average value of
everything returned in the salary column from the employee table.
Another example:
SELECT AVG(salary)
FROM employee;
WHERE title = 'Programmer';
This statement will return the average salary for all employees whose title is equal
to 'Programmer'
Example:
SELECT Count(*)
FROM employees;
This particular statement is slightly different from the other aggregate functions since there isn't a column supplied to the count function. This statement will return the number of rows in the employees table.
Review Exercises
- Select the maximum price of any item ordered in the items_ordered table. Hint: Select the maximum price only.
>
- Select the average price of all of the items ordered that were purchased
in the month of Dec.
- What are the total number of rows in the items_ordered table?
- For all of the tents that were ordered in the items_ordered table, what
is the price of the lowest tent? Hint: Your query should return the price only.
Answers to these Exercises
Enter SQL Statement here:
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