CURDATE(): This function returns the current date.

SELECT CURDATE();

YEAR(): extracts the year from a date

SELECT YEAR(CURDATE());

SUBSTR (): This SUBSTR() function in SQL is used to extract a substring from a string, starting from a specified position and optionally for a specified length.

SELECT SUBSTR('Hello World', 7, 5);

--This query will return 'World' (5 characters) start from 7th position

NVL(): This function in SQL is used to replace NULL values with a specified value.

SELECT NVL(employee_bonus, 0) AS bonus
FROM employees;

--if the employee_bonus column has a NULL value, it will be replaced with 0

CONCAT: It is used to combine multiple strings or columns into a single string.

Example:

Q. How to print first name and last name together?

Ans:

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