SELECT count(DISTINCT pettype) FROM pets
Find the number of distinct type of pets.
create table Student (
       StuID    	INTEGER PRIMARY KEY,
       LName		VARCHAR(12),
       Fname		VARCHAR(12),
       Age		INTEGER,
       Sex		VARCHAR(1),
       Major		INTEGER,
       Advisor		INTEGER,
       city_code	VARCHAR(3)
);
create table Has_Pet (
       StuID		INTEGER,
       PetID		INTEGER,
       FOREIGN KEY(PetID) REFERENCES Pets(PetID),
       FOREIGN KEY(StuID) REFERENCES Student(StuID)
);
create table Pets (
       PetID		INTEGER PRIMARY KEY,
       PetType		VARCHAR(20),
       pet_age INTEGER,
       weight REAL
);
INSERT into Student values ( 1001, 'Smith', 'Linda', 18, 'F', 600, 1121,'BAL');
INSERT into Has_Pet values ( 1001, 2001 );
INSERT into Pets values ( 2001, 'cat', 3, 12);
INSERT INTO Student VALUES [(1001, 'Smith', 'Linda', 18, 'F', 600, 1121, 'BAL'), (1002, 'Kim', 'Tracy', 19, 'F', 600, 7712, 'HKG')]
INSERT INTO Has_Pet VALUES [(1001, 2001), (1002, 2002)]
INSERT INTO Pets VALUES [(2001, 'cat', 3, 12.0), (2002, 'dog', 2, 13.4)]