Problem:

You are building a database and you have a field that can accept only certain responses. For example, there is a Gender column which accepts only M or F as values.

Solution:

Gender ENUM('M','F') not null

This means, the columns can take only one of the values explicitly listed in the column specification. Either F or M.

ENUM allows you to specify a restricted set of values the column can hold.

Multiple character values are also allowed.

Gender ENUM('Male','Female') not null

Complete Example:

1. Create a table:

CREATE TABLE Person (
   Name VARCHAR(25) NOT NULL,
   Gender ENUM('M','F') NOT NULL,
   Id INT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY
)

Insert a row:

INSERT INTO Person VALUES('John','M',NULL);