SQL · Theory

Boolean

Theory

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Boolean

MySQL treats 0 as false and 1 (or non-zero) as true in many boolean contexts. A TINYINT(1) column is a common ‘boolean’. TRUE and FALSE are aliases for 1 and 0.

WHERE passed; means WHERE passed <> 0. Prefer WHERE passed = 1 so readers don’t guess.

Trap — storing ‘yes’/‘no’ strings and comparing to TRUE.

On the example next to this theory — Boolean — wHERE combines predicates with AND/OR; LIKE does pattern match.

Exam tip

TINYINT(1) as 0/1. WHERE passed = 1;

Boolean — sample query

CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT, price REAL);
INSERT INTO products VALUES (1, 'Pen', 10), (2, 'Book', 200), (3, 'Bag', 50);
SELECT * FROM products
WHERE price BETWEEN 20 AND 150 AND name LIKE 'B%';

Boolean — wHERE combines predicates with AND/OR; LIKE does pattern match.

Short notes

Def0 false, non-zero true. TRUE=1 FALSE=0.
RulePrefer = 1 / = 0 on a TINYINT flag.
Trapyes/no strings as booleans.

CREATE TABLE products (id INTEGER PRIMARY KEY, name TEXT, price REAL); INSERT INTO products VALUES (1, 'Pen', 10), (2, 'Book', 200), (3, 'Bag', 50); SELECT * FROM products WHERE price BETWEEN 20 AND 150 AND name LIKE 'B%';

Boolean

Boolean — sample query

Short notes

Questions

Boolean

Boolean — sample query

Short notes

Questions