Absolutely! Let’s do a full in-depth guide on SQL Operators, categorized by types, with separate explanations and examples using the employees and departments tables. I’ll structure it for clarity and mastery.

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🌐 SQL Operators – Types, Uses, and Examples

In SQL, operators are symbols or keywords that perform operations on data values. They are broadly classified into 6 major types:

1. Arithmetic Operators

2. Comparison / Relational Operators

3. Logical Operators

4. String / Concatenation Operators

5. Special Operators

6. Subquery Operators

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1️⃣ Arithmetic Operators

Purpose: Perform mathematical calculations on numeric data.

Example – Employees Table

-- Increase salary by 10%
SELECT first_name, salary, salary * 1.10 AS new_salary
FROM employees;

-- Check if employee_id is even or odd
SELECT employee_id, employee_id % 2 AS remainder
FROM employees;

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2️⃣ Comparison / Relational Operators

Purpose: Compare two values and return TRUE/FALSE.

Example – Employees Table

-- Employees with salary between 3000 and 7000
SELECT first_name, salary
FROM employees
WHERE salary BETWEEN 3000 AND 7000;

-- Employees not in department 1 or 2
SELECT first_name, department_id
FROM employees
WHERE department_id NOT IN (1,2);

-- Employees whose last name starts with 'S'
SELECT first_name, last_name
FROM employees
WHERE last_name LIKE 'S%';

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3️⃣ Logical Operators

Purpose: Combine multiple conditions.

Example – Employees Table

-- Employees in department 1 or 2 with salary > 5000
SELECT first_name, salary, department_id
FROM employees
WHERE (department_id = 1 OR department_id = 2) AND salary > 5000;

-- Employees whose department does NOT exist in dept table
SELECT first_name, department_id
FROM employees e
WHERE NOT EXISTS (SELECT 1 FROM departments d WHERE d.department_id = e.department_id);

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4️⃣ String / Concatenation Operators

Purpose: Combine or manipulate string values.

Example – Employees Table

-- Full name
SELECT CONCAT(first_name, ' ', last_name) AS full_name
FROM employees;

-- Display salary info in sentence
SELECT CONCAT(first_name, ' earns $', salary) AS info
FROM employees;

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5️⃣ Special Operators

Purpose: Special conditions like range checks, set membership, pattern matching, NULL handling.

Example – Employees Table

-- Employees NOT between salary 3000 and 7000
SELECT first_name, salary
FROM employees
WHERE salary NOT BETWEEN 3000 AND 7000;

-- Employees with a manager
SELECT first_name, manager_id
FROM employees
WHERE manager_id IS NOT NULL;

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6️⃣ Subquery Operators

Purpose: Compare or filter based on subquery results.

Example – Employees Table

-- Employees with salary greater than any employee in department 2
SELECT first_name, salary
FROM employees
WHERE salary > ANY (SELECT salary FROM employees WHERE department_id = 2);

-- Employees in departments that exist in dept table
SELECT first_name, department_id
FROM employees e
WHERE department_id IN (SELECT department_id FROM departments);

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✅ Summary

SQL Operators Types:

1. Arithmetic – +, -, *, /, %

2. Comparison / Relational – =, !=, <, >, <=, >=, BETWEEN, IN, LIKE, IS NULL

3. Logical – AND, OR, NOT, ANY, ALL, EXISTS

4. String / Concatenation – CONCAT(), ||, +

5. Special – BETWEEN, NOT BETWEEN, IN, NOT IN, LIKE, NOT LIKE, IS NULL, EXISTS

6. Subquery – =, !=, IN, NOT IN, ANY, ALL, EXISTS