window functions

SQL AVG() for Beginners

July 23, 2023December 8, 2020 by Ian

In SQL, the AVG() function is an aggregate function that returns the average of all values in a given expression.

It can also be used to return the average of all distinct (unique) values in an expression.

The expression must be numeric (it cannot be character string, bit string, or datetime).

Below are some basic examples to demonstrate how it works.

SQL SUM() for Beginners

July 23, 2023December 8, 2020 by Ian

In SQL, the SUM() function is an aggregate function that returns the sum of all values in a given expression.

It can also be used to return the sum of all distinct (unique) values in an expression.

The expression must be numeric (it cannot be character string, bit string, or datetime).

Below are some basic examples to demonstrate how it works.

SQL MAX() for Beginners

July 23, 2023December 7, 2020 by Ian

In SQL, the MAX() function is an aggregate function that returns the maximum value in a given expression.

Below are some basic examples to demonstrate how it works.

SQL MIN() for Beginners

July 23, 2023December 7, 2020 by Ian

In SQL, the MIN() function is an aggregate function that returns the minimum value in a given expression.

Below are some basic examples to demonstrate how it works.

SQL COUNT() for Beginners

July 23, 2023December 7, 2020 by Ian

In SQL, the COUNT() function is an aggregate function that returns the number of items found in a group.

You can use COUNT() in multiple parts of a query. For example, you can use it in the SELECT list, or the HAVING clause when filtering groups.

MIN() – Find the Minimum Value in a Column in MySQL

July 21, 2023July 16, 2018 by Ian

The MySQL MIN() function is an aggregate function that returns the minimum value from an expression.

Typically, the expression would be a range of values returned as separate rows in a column, and you can use this function to find the minimum value from the returned rows. If there are no matching rows, MIN() returns NULL.

For example, you can use this function to find out which city has the smallest population out of a list of cities.

MAX() – Find the Maximum Value in a Column in MySQL

July 21, 2023July 16, 2018 by Ian

The MySQL MAX() function is an aggregate function that returns the maximum value from an expression.

Typically, the expression would be a range of values returned as separate rows in a column, and you can use this function to find the maximum value from the returned rows. If there are no matching rows, MAX() returns NULL.

For example, you can use this function to find out which city has the largest population out of a list of cities.

6 Ways to Check the Size of a Database in SQL Server using T-SQL

July 21, 2023May 27, 2018 by Ian

If you’re using a GUI tool, such as SSMS to manage your databases, you can easily check the size of your database by clicking your way through the GUI (right-click the database, point to Reports, then Standard Reports, and then click Disk Usage).

However, if you prefer to use T-SQL to manage your databases, you’ll need to run a query that returns this information.

This article presents six ways to check the size of a SQL Server database using T-SQL.

AVG() – Calculate the Average Value of a Column in MySQL

July 21, 2023May 24, 2018 by Ian

When using MySQL, you can use the AVG() function to calculate the average value from a range of values.

For example, you can use this function to find out what the average city population is for a given country or state. Given a country will have many cities, each with different populations, you can find out what the average is between them. One city might have a population of say, 50,000 while another has a population of 500,000. The AVG() function will calculate the average for you.