…Aggregate functions are functions that operate on a…set of rows rather than row by row.…For example, we'll be using the world database.…And we'll start with a simple example of an…aggregate function that we're all familiar with the Count function.…So, I'll select COUNT with an asterisk in the parenthesis.…FROM the country table.…And when I press go, you see there are 239 rows in the country table.…So this returns one result for a number of rows.…
There's 239 rows but there's only one result for the count.…The asterisk is a special case for the count…function that will count all the rows in a table.…If instead, you specify a column.…COUNT will count all the non-null values in that column.…So if I put in here population, which I know has a view null values…in it, you notice we get a smaller value; instead of 239 we get 232.…And those are the non-null values in the population column.…
The GROUP BY clause, I'll put an asterisk back in over here and we'll…specify a group by may be used to group rows for use with aggregate functions.…
- Writing queries
- Creating and updating databases and tables
- Using MySQL built-in functions
- Sorting and filtering data
- Updating tables with triggers
- Working with subselects and views
- Creating and using a stored function
Skill Level Beginner
1. Installing and Configuring the Test Environment
2. Basic Syntax
3. Creating a Database
4. MySQL Data Types
5. MySQL Functions
8. Subselects and Views
9. Stored Routines
10. PHP's PDO Interface with MySQL
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