Is this the proper way to do boolean test in SQL?

sql

boolean-logic

database-quirks

sql-standards

byAlex Kataev·Sep 16, 2024

Perform Boolean testing in SQL by using the WHERE clause for direct checks or CASE for conditional logic. Here's a quick look:

-- Direct Boolean check, or as we call it, "Keep it simple, silly!"
SELECT * FROM table_name WHERE is_active; -- Assumes `is_active` is a Boolean column.

-- Conditional logic with CASE:
-- Also known as "Making things a bit more interesting!"
SELECT *, CASE WHEN is_active THEN 'Yes' ELSE 'No' END as IsActiveText FROM table_name;

These snippets focus on Boolean-based responses in-line with SQL standard and readability best practices.

In PostgreSQL, you might meet the John Cena of boolean syntax - you can't see it, but it's there:

-- PostgreSQL direct Boolean check:
SELECT * FROM table_name WHERE is_active;

But, remember not all WWE superstars are John Cena! Some databases might want you to explicitly compare with true or false.

Boolean, integers, or char?

Your SQL database can represent Boolean values in several avatars, such as bit fields (0 or 1), or char(1) types ('Y'/'N'). So, it's key to know your database's avatar for Boolean.

Integer bit fields

If your database treats booleans like integers, squeeze out the truth with 1 and 0:

SELECT * FROM users WHERE is_active = 1; -- Active users
SELECT * FROM users WHERE is_active = 0; -- Inactive users or 'The Lazies'

Avoid mixing integers and strings, or it'll be like oranges and apples - chaos!

Char(1) types

If your database is a fan of Yes/No drama:

SELECT * FROM users WHERE is_subscribed = 'Y'; -- Subscribed users

Clarity and tool compatibility are the perks of using char(1) types. But remember, 'Y' is NOT 'y' here, case matters!

Databases and their boolean quirks

Different databases have different tastes for boolean candy. Don’t try to feed a PostgreSQL candy to MySQL, or it may choke:

PostgreSQL Presents glorified 'true'

PostgreSQL lets you show-off bare boolean fields:

-- PostgreSQL's matinee idol:
SELECT * FROM events WHERE is_public;

MySQL's 1's and 0's Apetite

MySQL has an appetite for tinyint(1):

-- MySQL's favorite dish:
SELECT * FROM products WHERE is_available = 1;

This 1 trick makes MySQL go gaga!

SQL Server's Bit-sized Feast

SQL Server hosts a bit-party, with bits for true and false:

-- SQL Server's favorite bit:
SELECT * FROM job_queue WHERE is_processed = 'true';

Being drama queen SQL Server enjoys a true performance rather than dull 1s or 0s.

NOT Operator Etiquette

Though useful, the NOT operator can turn your SQL into a riddle (which we all love, right?):

SELECT * FROM emails WHERE NOT is_spam; --Believe it or not!

Just saying NO can make your intent clearer. So, limit your 'NOT's, like sweets!

Common issues and remedies

Here are some common boo-boos and their antidotes:

Null is not your friend

Treat NULL values like a cat treats a cucumber. Beware!!!

SELECT * FROM tasks WHERE is_completed IS NOT NULL AND is_completed = FALSE;

Implicit conversions

Implicit conversions are like an unexpected guest. Ensure data types align:

SELECT * FROM messages WHERE read_count <> 0; -- 'String' lantern won't light in 'integer' socket

Portability and standards

When in Rome, speak Roman (or was it Latin?). Align with SQL standards for portability:

UPDATE accounts 
SET is_verified = 
CASE WHEN verification_code = input_code THEN TRUE ELSE FALSE END;

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