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sex represents whether a student is a boy or a girl. It's an ENUM (enumeration) column, which means it can take on only one of the values listed in the column specification: 'F' for female or 'M' for male. ENUM is useful when you have a restricted set of values that a column can hold. We could have used CHAR(1) instead, but ENUM makes it more explicit what the column values can be. If you forget what the possible values are, issue a DESCRIBE tbl_name statement. For an ENUM column, MySQL will display the list of legal enumeration values.
By the way, values in an ENUM column need not be just a single character. The type column could have been declared as something like ENUM('female','male') instead.
student_id is an integer column that will contain unique student ID numbers. Normally, you'd probably get ID numbers for your students from a central source, such as the school office. We'll just make them up, using an AUTO_INCREMENT column that is declared in much the same way as the member_id column that is part of the member table created earlier.
Note that if you really were going to get student ID numbers from the office rather than generating them automatically, you could declare the student_id column without the AUTO_INCREMENT attribute. But leave in the PRIMARY KEY clause to disallow duplicate IDs.
The event table looks like this:
CREATE TABLE event
(
date DATE NOT NULL,
type ENUM('T','Q') NOT NULL,
event_id INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY (event_id)
);
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