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.
Continue readingIn 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.
Continue readingIn 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.
Continue readingIn 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.
This page contains a list of aggregate functions that are available in SQLite by default.
Continue readingSQLite has a group_concat() function that allows you to concatenate multiple results returned for a column into one.
This is sometimes referred to as “string aggregation”.
For example, when querying a database, instead of having each column’s value output in a new row, you can use group_concat() to have them output as a comma separated list.
If you know about the avg() function in SQLite, you’re probably aware that it returns the average of all non-NULL X within a group.
But did you know you can add the DISTINCT keyword to this function?
If you add the DISTINCT keyword, avg() will calculate its results based on distinct values only. This is essentially the same as removing duplicate values and then calculating the average on the remaining values.
In SQLite, the Sum() function accepts an optional DISTINCT keyword that enables you to add just the distinct values in the group. That is, it removes any duplicates from its calculation.
So if there are say, three rows that contain 10, only one of those rows will be included in the results.
Continue readingWhen using the count() function in SQLite, you might find yourself in the situation where you only want to count distinct values. That is, you don’t want duplicate values to be counted multiple times.
SQLite has a function called sum() and another function called total(). Both functions do pretty much the same thing – they return the sum of all non-NULL values in a group.
But there is a subtle difference between these two functions.
The difference is in the way they handle NULL inputs.
Continue reading