Sql - IF EXISTS UPDATE ELSE INSERT INTO

UNIQUE, the Guardian of Data

Preserving data integrity is an unsung hero. By applying a UNIQUE constraint on subs_email, we ensure a Highlander scenario: "There can be only one... of each email address". This sets up the stage for the upsert operation, where update and insert form a dynamic duo.

-- Who said database admins don't have fun?
INSERT INTO subscribers (subs_email, subs_name) 
VALUES (?, ?)
ON DUPLICATE KEY UPDATE subs_name = VALUES(subs_name);
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Parameterize it all to build a fortress against SQL injection:

$stmt = $pdo->prepare($insertQuery);
$stmt->execute([$email, $name]);
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This method doesn't only slim your code but propels performance, too – no need for two trips to the server anymore!

Data Privacy and Your Application

Make sure to parameterize any SQL query that's functioning as an interface element; it's a lifesaver against SQL injection attacks, the web's supervillain.

Choosing the Right SQL Pattern

Pick the SQL pattern that aligns with your project's requirements. The MERGE statement is SQL Server's regular but can be rehashed for other databases. MySQL has a unique INSERT ... ON DUPLICATE KEY UPDATE syntax, whereas some others use UPSERT.

AUTO_INCREMENT, A Double-Edged Sword

Tread lightly on AUTO_INCREMENT fields. Why? The upsert pattern could bump up the auto-increment counter, even if there's no new insertion. Let's get hands-on and test our specific scenarios to witness how our databases react.

Safety Measures for Database Connections

Secure your database connection and conduct efficient, safe URL parsing - your first line of defense against threats.

Database Choice implications

Depending on your database choice, the upsert method might vary. Both SQLite and PostgreSQL have unique syntax and implementation:

SQLite:

-- SQLite taking a page from the strength of its rival PostgreSQL
INSERT INTO subs (email, name) VALUES (?, ?)
ON CONFLICT(email) DO UPDATE SET name = excluded.name;
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PostgreSQL:

-- PostgreSQL doing its thing, in style
INSERT INTO subs (email, name) VALUES (?, ?)
ON CONFLICT (email) DO UPDATE SET name = EXCLUDED.name;
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