How to add input validation to a stored procedure?

Question

SQL

Good day. I have such a problem. There is a task: To develop stored procedures for adding/changing/deleting data. It is necessary to add checks of input data to the procedures according to the table above. (data type, NOT NULL condition, data uniqueness) If incorrect data is entered, output text with a readable error.

There is a code with a procedure:

CREATE PROCEDURE add_product (a INT, b TIMESTAMP, c VARCHAR(20), d VARCHAR(50), e INT, f INT)
LANGUAGE SQL
AS $$
INSERT INTO sales (ID, Sale_time, Pharmacy, product, Number_of_packages, Price)
VALUES (a, b, c, d, e, f);
$$;

How to add input validation to this procedure? Thank you in advance

Answer 1

Judging by the code you have MySql.
Here are the details:
https://www.w3resource.com/mysql/mysql-procedure.php
And here is a small example:
https://www.tutorialspoint.com/how-to-display-mess...