DBMS – Page 306

3 Ways to Replace NULL with “N/A” in SQLite

May 28, 2020May 13, 2020 by Ian

In SQLite, if you need to replace NULL results with text such as “N/A”, “None”, or even the text “NULL”, you can use one of the three solutions below.

List all Indexes in an SQLite Database

August 5, 2024May 13, 2020 by Ian

In this article I outline two ways to return a list of indexes in an SQLite database.

The first (and most obvious) method is to use the .indexes dot command. The second method is to query the sql_master table.

How AUTOINCREMENT Works in SQLite

May 28, 2020May 12, 2020 by Ian

In SQLite, an AUTOINCREMENT column is one that uses an automatically incremented value for each row that’s inserted into the table.

There are a couple of ways you can create an AUTOINCREMENT column:

You can create it implicitly when you define the column as INTEGER PRIMARY KEY.
You can create it explicitly with the AUTOINCREMENT keyword. One downside of this method is that it uses extra CPU, memory, disk space, and disk I/O overhead.

Both methods cause the column to use an incrementing value each time a new row is inserted with NULL in that column.

However, there are some subtle differences between how each method works.

Tweak your Avg() Results in SQLite with the DISTINCT Keyword

May 28, 2020May 11, 2020 by Ian

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.

How to Add Just the Distinct Values with SQLite Sum()

May 28, 2020May 10, 2020 by Ian

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.

Remove Duplicates from Count() Results in SQLite

May 28, 2020May 10, 2020 by Ian

When 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.

List all Temporary Tables in SQLite

November 15, 2025May 10, 2020 by Ian

As with most things in SQLite, there’s more than one way to get a list of temporary tables in a database.

Here I present two ways to return temporary tables in SQLite.

2 Ways to List the Tables in an SQLite Database

November 15, 2025May 9, 2020 by Ian

Here are two ways to return a list of tables in all attached databases in SQLite.

The first method returns all tables and views for all attached databases.

The second method gives you the option of returning both tables and views, or just tables, but only for the primary database.

Update Dec 2021: Since writing this article, SQLite has introduced another option, which I’ve listed as a bonus third option at the end of this article.

SQLite Sum() vs Total(): What’s the Difference?

May 28, 2020May 8, 2020 by Ian

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.

How SQLite Total() Works

May 28, 2020May 8, 2020 by Ian

In 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).