How to do IF NOT EXISTS in SQLite

Patterns and practices for optimizing data insertion

The simple approach is great, however, SQLite is a versatile tool, providing several paths to achieve the same goal. Let's explore these paths to give you multiple options to reach your destination.

The "not exists" select pattern

When wrestling with tricky conditions or when your table lacks a UNIQUE constraint, rely on this solid mate:

INSERT INTO example (unique_column)
SELECT 'PotentialUniqueValue'
WHERE NOT EXISTS (
    SELECT 1 FROM example WHERE unique_column = 'PotentialUniqueValue'
);


This method checks if PotentialUniqueValue is already part of the unique club in unique_column. If not, it cordially invites it to join, else it prefers to maintain status quo.

Plan your tables wisely

Craft your tables with the necessary constraints, so they can smoothly tackle SQLite's conflict resolution clauses such as IGNORE or REPLACE. After all, a poorly designed table stands on shaky ground!

The "insert or replace" for the undecided

When you're not sure whether to invite new data or update an existing one, SQLite provides the INSERT OR REPLACE command, perfect for those indecisive moments.

CREATE TABLE example (
    id INTEGER PRIMARY KEY,
    unique_column TEXT UNIQUE,
    data TEXT
);

-- Let's add 'NewData' or replace, we'll cross that bridge when we come to it!
INSERT OR REPLACE INTO example (unique_column, data) VALUES ('UniqueValue', 'NewData');


This command is the perfect butler, ensuring records are updated if a duplicate candle (ahem unique key) is found on the dinner table!

Learning to wrestle with SQLite's capabilities

When you've tamed the horse, it’s easy to learn its tricks. Here's how you adapt your SQL knowledge to embrace SQLite's capabilities, especially if you're moving from MS SQL Server.

The "on conflict" resolver

Say you're dealing with a table that needs to handle multiple giants in one castle. Define custom conflict resolution strategies using the ON CONFLICT clause:

CREATE TABLE example (
    id INTEGER PRIMARY KEY,
    unique_column TEXT,
    UNIQUE (unique_column) ON CONFLICT IGNORE
);


This setup gracefully sidesteps insertion errors when potential duplicates charge in, staying true to the principles of IF NOT EXISTS.

Doing the math for existence checks

Sometimes, in the midst of complex calculations, a numerical check for existence is what you need:

SELECT (1-EXISTS(SELECT 1 FROM table WHERE condition)) AS NonExistenceFlag;


Here, NonExistenceFlag faithfully returns 1 if the condition isn't found lurking in the shadows, which could be handy when crunching complex reports.

SQLite Constraints 101

To maintain data integrity and intended behavior, understand the wide array of constraints and conflict resolutions SQLite has up its sleeve. These include PRIMARY KEY, UNIQUE, FOREIGN KEY, and the respective ON CONFLICT clauses.