WHERE Clause in MySQL

The WHERE clause in MySQL is used to filter records in a SELECT, UPDATE, DELETE, or INSERT statement based on a condition.

1. Syntax

SELECT column1, column2 FROM table_nameWHERE condition;

🔹 Conditions can include:
✅ Comparisons (=, >, <, >=, <=, !=)
✅ Logical Operators (AND, OR, NOT)
✅ Wildcards (LIKE)
✅ Lists (IN)
✅ Ranges (BETWEEN)

2. Example Table: employees

3. Using WHERE in SELECT

SELECT * FROM employees WHERE department = 'IT';

✅ Result:

4. Using WHERE with Comparison Operators

SELECT * FROM employees WHERE salary > 5500;

✅ Finds employees with salary greater than 5500.

5. Using WHERE with AND

SELECT * FROM employees WHERE department = 'IT' AND salary > 5500;

✅ Finds employees in IT with salary greater than 5500.

6. Using WHERE with OR

SELECT * FROM employees WHERE department = 'IT' OR department = 'HR';

✅ Finds employees in either IT or HR.

7. Using WHERE with BETWEEN

SELECT * FROM employees WHERE salary BETWEEN 5000 AND 6000;

✅ Finds employees with salary in the range 5000-6000.

8. Using WHERE with IN

SELECT * FROM employees WHERE department IN ('IT', 'Finance');

✅ Finds employees in IT or Finance departments.

9. Using WHERE with LIKE (Wildcard Search)

SELECT * FROM employees WHERE name LIKE 'A%';

✅ Finds employees whose names start with "A".

10. Using WHERE in UPDATE

UPDATE employees SET salary = 6500 WHERE emp_id = 1;

✅ Updates Alice’s salary to 6500.

11. Using WHERE in DELETE

DELETE FROM employees WHERE department = 'HR';

✅ Removes all employees from the HR department.

Key Takeaways

✅ The WHERE clause filters records based on conditions.
✅ Supports comparisons, logical operators, wildcards, lists, and ranges.
✅ Used with SELECT, UPDATE, and DELETE statements.
✅ Always use WHERE in UPDATE and DELETE to avoid modifying all rows!