Logical Operators

Logical operators combine multiple conditions in one WHERE clause.

They let you express real-world rules clearly.

Core Concepts

flowchart TD
  A[Condition A] --> D{Logical operator}
  B[Condition B] --> D
  D -->|AND| E[Both must be true]
  D -->|OR| F[Either can be true]
  D -->|NOT| G[Invert condition]

Operator	Meaning	Example
AND	Both conditions true	status='open' AND severity>=3
OR	At least one true	status='open' OR severity>=5
NOT	Negate condition	NOT status='closed'

AND Example

SELECT title, status, severity
FROM issues_where
WHERE status = 'open' AND severity >= 4;

title	status	severity
Crash on save	open	5

OR Example

SELECT title, status, severity
FROM issues_where
WHERE status = 'closed' OR severity >= 5;

title	status	severity
UI typo	closed	1
Crash on save	open	5

Code Examples

-- Use parentheses to make precedence explicit.
SELECT issue_id, title
FROM issues_where
WHERE (status = 'open' AND severity >= 3)
   OR title = 'UI typo';

issue_id	title
1	Login bug
2	UI typo
3	Crash on save

SQLite-Specific Nuances

SQLite Nuance

Operator precedence applies in SQLite, so AND is evaluated before OR unless parentheses change grouping.

Common Pitfalls / Best Practices

Pitfall

Writing mixed AND/OR conditions without parentheses and getting unexpected results.

Best Practice

Use parentheses whenever conditions are non-trivial, even if precedence rules would still work.

Quick Challenge

Return issues where status is open but severity is not 3.

View Solution

SELECT issue_id, title, severity
FROM issues_where
WHERE status = 'open' AND NOT severity = 3;

issue_id	title	severity
3	Crash on save	5