Expressions

MySQL expressions are combinations of values, operators, and functions that evaluate to a single value. They are used in conditions, calculations, and dynamic query construction.

Common Uses of MySQL Expressions

1. Arithmetic Expressions: Perform calculations.
2. String Expressions: Manipulate text.
3. Logical Expressions: Create conditions.
4. Date Expressions: Handle date operations.
5. Comparison Expressions: Compare values.

Examples

1. Arithmetic Expression
    

   SELECT price * quantity AS total FROM orders;

   Explanation: Calculates the total price for each order.

2. String Expression
    

   SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;

   Explanation: Combines first_name and last_name into a full name.

3. Logical Expression
    

   SELECT * FROM orders WHERE amount > 50 AND status = 'Paid';

   Explanation: Filters orders with amount greater than 50 and status Paid.

4. Date Expression
    

   SELECT CURDATE() - INTERVAL 30 DAY AS last_month;

   Explanation: Calculates the date 30 days ago.

5. Comparison Expression
    

   SELECT * FROM employees WHERE salary BETWEEN 3000 AND 5000;

   Explanation: Filters employees with salaries between 3000 and 5000.