- SQL Basics
- SQL Introduction
- SQL Syntax
- SQL Sample Database
- SQL SELECT
- SQL WHERE
- SQL ORDER BY
- SQL DISTINCT
- SQL LIMIT
- SQL FETCH
- SQL AND
- SQL OR
- SQL BETWEEN
- SQL IN
- SQL LIKE
- SQL IS NULL
- SQL Comparison Operators
- SQL Logical Operators
- SQL Alias
- SQL CASE
- Joins and Subqueries
- SQL INNER JOIN
- SQL LEFT JOIN
- SQL RIGHT JOIN
- SQL FULL OUTER JOIN
- SQL SELF JOIN
- SQL CROSS JOIN
- SQL Subquery
- SQL Correlated Subquery
- SQL UNION
- SQL INTERSECT
- SQL EXCEPT
- Aggregate Functions
- SQL AVG
- SQL COUNT
- SQL MAX
- SQL MIN
- SQL SUM
- SQL GROUP BY
- SQL HAVING
- SQL ROLLUP
- SQL CUBE
- SQL GROUPING SETS
- Database Management
- SQL CREATE DATABASE
- SQL ALTER DATABASE
- SQL DROP DATABASE
- SQL BACKUP DATABASE
- SQL SHOW DATABASES
- SQL SELECT DATABASE
- Table Management
- SQL CREATE TABLE
- SQL ALTER TABLE
- SQL ADD COLUMN
- SQL DROP COLUMN
- SQL DROP TABLE
- SQL TRUNCATE TABLE
- SQL SHOW TABLES
- SQL RENAME TABLE
- SQL Constraints
- SQL Primary Key
- SQL Foreign Key
- SQL UNIQUE Constraint
- SQL CHECK Constraint
- SQL NOT NULL Constraint
SQL Logical Operators
SQL logical operators are used to combine multiple conditions in a query. They help filter records based on whether the combined conditions are true or false.
List of SQL Logical Operators
Key Features of Logical Operators
1. AND Operator
The AND operator is used to filter rows where all the conditions are true.
Example:
SELECT name, salary, age
FROM employees
WHERE salary > 3000 AND age < 40;
- Retrieves employees with a salary greater than 3000 and age less than 40.
2. OR Operator
The OR operator is used to filter rows where at least one condition is true.
Example:
SELECT name, salary, age
FROM employees
WHERE salary > 5000 OR age < 25;
- Retrieves employees with a salary greater than 5000 or age less than 25.
3. NOT Operator
The NOT operator reverses the result of a condition.
Example:
SELECT name, salary
FROM employees
WHERE NOT salary = 5000;
- Retrieves employees where the salary is not equal to 5000.
Combining Logical Operators
You can combine AND, OR, and NOT in a single query to create complex conditions. Use parentheses () to group conditions for clarity and to determine the order of evaluation.
Example 1: Combining AND and OR
SELECT name, salary, department
FROM employees
WHERE department = 'IT' AND (salary > 4000 OR age < 30);
- Retrieves employees from the IT department who either have a salary greater than 4000 or are younger than 30.
Example 2: Using NOT with OR
SELECT name, salary
FROM employees
WHERE NOT (salary < 3000 OR salary > 7000);
- Retrieves employees where the salary is not less than 3000 and not greater than 7000 (i.e., between 3000 and 7000).
Logical Operator Precedence
Logical operators in SQL follow a specific order of precedence:
- NOT
- AND
- OR
To override precedence, use parentheses () to explicitly specify the order.
Example:
SELECT name
FROM employees
WHERE NOT (age > 40 AND salary < 3000);
- The condition inside the parentheses is evaluated first.
Summary
SQL logical operators (AND, OR, and NOT) allow you to filter records based on multiple conditions. Use AND to combine conditions where all must be true, OR for at least one true condition, and NOT to negate a condition. Parentheses can be used to clarify and control the evaluation order for complex queries.