Logical Operators

Logical operators let you combine multiple conditions in a WHERE clause, making your filters more flexible and precise.

Main Logical Operators

Operator	Description	Example
AND	All conditions must be true	membership_type = 'student' AND has_overdue_books = 'no'
OR	At least one condition must be true	membership_type = 'guest' OR number_of_books > 3
NOT	Reverses or excludes a condition	NOT has_overdue_books = 'yes'

AND Operator Example

The AND operator filters rows where all conditions must be true.

Filter: Students with no overdue books

SELECT name, membership_type
FROM library_members
WHERE membership_type = 'student' AND has_overdue_books = 'no';

This query returns students who do not have any overdue books.

OR Operator Example

The OR operator filters rows where at least one condition is true.

Filter: Guests or those with many books

SELECT name, number_of_books
FROM library_members
WHERE membership_type = 'guest' OR number_of_books > 3;

This query returns either guests or anyone with more than 3 books checked out.

NOT Operator Example

The NOT operator filters out rows where the condition is true, returning only those that do not match.

Filter: Exclude members with overdue books

SELECT name
FROM library_members
WHERE NOT has_overdue_books = 'yes';

This query returns only members who do not have overdue books.

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