🔹 1. Operators in MySQL

(A) Arithmetic Operators

Used for calculations.

SELECT 10 + 5;   -- 15
SELECT 10 - 5;   -- 5
SELECT 10 * 5;   -- 50
SELECT 10 / 5;   -- 2
SELECT 10 % 3;   -- 1 (modulus)

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(B) Comparison Operators

Used in WHERE clauses.

=      → Equal
<> or != → Not equal
>      → Greater than
<      → Less than
>=     → Greater or equal
<=     → Less or equal
BETWEEN a AND b
LIKE 'A%'      → Starts with A
IN (x,y,z)     → Matches one of

Example:

SELECT * FROM employees WHERE age BETWEEN 25 AND 40;

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(C) Logical Operators

Combine conditions.

AND     -- Both conditions true
OR      -- Either condition true
NOT     -- Negates condition

Example:

SELECT * FROM employees
WHERE age > 30 AND city = 'Delhi';

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(D) Bitwise Operators

Operate on bits.

& (AND), | (OR), ^ (XOR), ~ (NOT), << (Left shift), >> (Right shift)

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(E) Other Operators

• IS NULL, IS NOT NULL

• EXISTS (subquery)

• ANY, ALL (used with subqueries).

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🔹 2. Clauses in MySQL

A clause is a keyword in SQL that adds conditions or modifies queries.

(A) WHERE

Filters rows.

SELECT * FROM employees WHERE salary > 50000;

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(B) ORDER BY

Sorts results.

SELECT * FROM employees ORDER BY salary DESC;

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(C) GROUP BY

Groups rows for aggregate functions (COUNT, SUM, AVG, MAX, MIN).

SELECT department, COUNT(*) 
FROM employees
GROUP BY department;

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(D) HAVING

Filters groups (used with GROUP BY).

SELECT department, COUNT(*)
FROM employees
GROUP BY department
HAVING COUNT(*) > 5;

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(E) LIMIT

Restricts number of rows returned.

SELECT * FROM employees LIMIT 5;

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(F) DISTINCT

Removes duplicates.

SELECT DISTINCT city FROM employees;

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(G) FROM / JOIN

Defines source tables and joins.

SELECT e.name, d.dept_name
FROM employees e
JOIN departments d ON e.dept_id = d.id;

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✅ Quick Summary

• Operators: Arithmetic (+, -, *, /), Comparison (=, <, >, BETWEEN, LIKE), Logical (AND, OR, NOT).

• Clauses:

  • WHERE → Filter rows.

  • ORDER BY → Sort.

  • GROUP BY → Aggregate.

  • HAVING → Filter groups.

  • LIMIT → Restrict rows.

  • DISTINCT → Remove duplicates.