Beginner learning sql joins in mySQL - sql

Question

I have created 3 tables: dog, customer and owner. It is a many to one relationship with many dogs owned by 1 customer.
CREATE TABLE dog
(
DogID int(6) NOT NULL,
DogName varchar(15),
medicalID int (6),
Gender character(1) check(gender in ('m', 'f')),
Age int(2),
Breed varchar(15),
size character (1) check(size in ('s', 'm', 'l')),
primary key (DogID));
CREATE TABLE Owns
(
DogID int (6)primary key,
CustomerID int (6),
foreign key (CustomerID) references customer (CustomerID),
foreign key (DogID) references dog (DogID));
CREATE TABLE customer
(
CustomerID int(6) NOT NULL,
FirstName varchar(15),
Surname varchar(15),
Address varchar(225),
email varchar (30),
TelNo varchar (15),
MobNo Varchar (15),
EmergencyName varchar (40),
EmergencyPhoneNo varchar(15),
primary key (CustomerID));
I have queried with but nothing is returned.
select dog.dogName
from dog, owns, customer
where owns.dogID = dog.dogId
and customer.customerID = owns.customerID
and customer.FirstName = "CustomersName";

Answer 1

You created the tables, now you need to INSERT the data.
INSERT INTO dog(<fields>) VALUES(<values>);

Answer 2

If you have successfully created the tables the next step is to put some data in them. Otherwise you won't get anything back from your query. You need to insert a record into the dog and customer tables and associate them via the owns table. After performing those 3 inserts you should be able to join on their keys and query for data.
For example:
insert into dog(DogID, DogName, medicalID, Gender, Age, Breed, Size) values ('111111', 'Spike', '111111', '12', 'Wolf', 'l' );
insert into customer ( CustomerID, FirstName, Surname, Address, email, TelNo, MobNo, EmergencyName, EmergencyPhoneNo ) values ( '222222', 'Abe', 'Lincoln', '123 Street', 'blah#blah.com', '8675309', '8675309', 'Bob', '8675309' );
insert into owns ( DogID, CustomerID ) values ( '111111', '222222' );
select DogName from dog as d
join owns as o on o.DogID = d.DogID
join customer as c on c.CustomerId = o.CustomerID
where c.FirstName = 'Abe';
Note that your syntax may be slightly different. I've been using Oracle for a while.