And so the DATETIMEs came to pass, and the light shined through the best part of SQL, functions. There are quite a bit of functions, and you might actually use the majority of them. I will just cover a basic overview of how to use a few functions, so you can easily use the rest when your tinkering around in SQL. Count, sum, and average are possibly the most common and in that order. However, sometimes you will use super helpful functions like max and min. Let’s discover what they look like, then we’ll use them.
Common SQL Functions
- count() – counts the number of records returned from the query
- sum() – adds the values in records returned from the query together
- avg() – averages values in records returned from the query
- max() – finds the highest value in all of the records returned from the query
- min() – finds the lowest value in all of the records returned from the query
Our “Users” Table:
SELECT COUNT(*) FROM Users
As you can see, all COUNT() does is count the values in the column specified inside the parentheses. However, we used the * wildcard, so it just counted all records.
SELECT SUM(views) FROM Users WHERE id <= 2
Now, we can use the SQL Functions on columns. We said give us the sum, sum(), of our views column, but only where the column id is less than or equal to 2. The 250 is the sum of Hillary and Al’s views because their id is less than or equal to 2. Note: math functions in SQL won’t do so well with strings.
SELECT AVG(views) FROM Users WHERE id >= 2
The SQL Function average, avg(), tells SQL to crunch our numbers in the views column and give us the average, but only where the id is greater than or equal to 2. This only averages George and Al’s views, which gives us 225.
SELECT MAX(views) FROM Users
So, the SQL Function max, obviously short for maximum, returns 300 because it is the highest number in our views column.
SELECT MIN(views) FROM Users
Exactly on the opposite spectrum of is the MIN(), short for minimum, SQL Function. This function grabs the lowest value of our views column.
And that’s all folks. Feel free to play around with the other SQL functions