SQLite 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 readingIn SQLite, the total() function returns the sum of all non-NULL values in a group.
If there are no non-NULL values, then it returns 0.0.
This function is similar to the sum() function, except in the way it handles NULL inputs. When there are no non-NULL values, then sum() returns NULL (instead of 0.0 like the total() function returns).
The SQLite sum() function returns the sum of all non-NULL values in a group.
If there are no non-NULL values, then it returns NULL.
This function basically enables you to add up all the values in a result set or a table.
Continue readingThe SQLite min() function returns the minimum non-NULL value from all values in a group.
The minimum value is the value that would appear first in a query that uses an ORDER BY clause on the same column.
The SQLite max() function returns the maximum value from all values in a group.
The maximum value is the value that would appear last in a query that uses an ORDER BY clause on the same column.
The SQLite avg() function returns the average value of all non-NULL values within a group.
It accepts one argument, which is the value or group of values.
Continue reading