NULLand NOTNULLCode

Try inserting a cat without an age:

INSERT INTO cats(name) VALUES('Alabama');

SELECT * FROM cats;

Try inserting a nameless and ageless cat:

INSERT INTO cats() VALUES();

Define a new cats2 table with NOTNULLconstraints:

CREATE TABLE cats2
  (
    name VARCHAR(100) NOT NULL,
    age INT NOT NULL
  );

DESC cats2;

Now try inserting an ageless cat:

INSERT INTO cats2(name) VALUES('Texas');

View the new warnings:

SHOW WARNINGS;

SELECT * FROM cats2;

Do the same for a nameless cat:

INSERT INTO cats2(age) VALUES(7);

SHOW WARNINGS;