USE test; 

-- 1. Add a primary key to the id fields in the pets and people tables.

ALTER TABLE people
ADD PRIMARY KEY (id);

DESCRIBE pets;
DESCRIBE people;

-- 2. Add a foreign key to the owner_id field in the pets table referencing the id field 
-- in the people table. 

ALTER TABLE pets 
ADD CONSTRAINT FK_PetsOwner 
FOREIGN KEY (owner_id) REFERENCES people(id);

-- 3. Add a column named email to the people table. 

ALTER TABLE people
ADD COLUMN email VARCHAR(20);

-- 4. Add a unique constraint to the email column in the people table.

ALTER TABLE people
ADD CONSTRAINT u_email UNIQUE (email);

-- 5. Rename the name column in the pets table to ‘first_name’.

ALTER TABLE pets CHANGE `name` `first_name` VARCHAR(20);

-- 6. Change the postcode data type to CHAR(7) in the addresses table.

ALTER TABLE addresses MODIFY postcode CHAR(7);

DESCRIBE addresses;