inner join gives in mysql gives error code 1052 - mysql

Question

I created a database with following tables :
CREATE SCHEMA IF NOT EXISTS `facturatiedatabase` ;
USE `facturatiedatabase` ;
DROP TABLE IF EXISTS tblAddress ;
DROP TABLE IF EXISTS tblContact ;
DROP TABLE IF EXISTS tblCustomers ;
CREATE TABLE tblCustomers (
customerID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
firstname VARCHAR(30) NOT NULL,
lastname VARCHAR(30) NOT NULL,
vat VARCHAR(30) NOT NULL,
customerVisible varchar(1) NOT NULL DEFAULT 'T'
) ENGINE=InnoDB;
CREATE TABLE tblContact (
contactID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
email VARCHAR(100),
phone VARCHAR(100),
customerID int,
CONSTRAINT FK_customerID_Contact FOREIGN KEY (customerID) REFERENCES tblCustomers(customerID)
) ENGINE=InnoDB;
CREATE TABLE tblAddress (
addressID INT NOT NULL AUTO_INCREMENT PRIMARY KEY,
street VARCHAR(100),
houseNumber VARCHAR(15),
city VARCHAR (100),
country VARCHAR (100),
customerID int,
CONSTRAINT FK_customerID_Adress FOREIGN KEY (customerID) REFERENCES tblCustomers(customerID)
) ENGINE=InnoDB;
INSERT INTO tblCustomers (firstname, lastname,vat)
VALUES ("John","Doe","UV45856855");
INSERT INTO tblContact (customerID,phone, email)
VALUES ((SELECT DISTINCT LAST_INSERT_ID() FROM tblCustomers), "0000001","Johndoe#gmail.com");
INSERT INTO tblAddress (customerID,street,housenumber,city,country)
VALUES ((SELECT DISTINCT LAST_INSERT_ID() FROM tblCustomers), "berkenlaan","1a","Harelbeke","Belgie");
But when i try following inner join it gives me the following error :
LIMIT 0, 1000 Error Code: 1052. Column 'customerID' in field list is ambiguous 0.000 sec.
SELECT customerID, firstname, lastname, vat,email
FROM tblCustomers
INNER JOIN tblContact on tblCustomers.customerID = tblContact.contactID

Answer 1

The error message says it all: the column name customerID is contained in both tables. So which value should mysql select? That is ambiguous, therefore the error.
Have a try with this variant:
SELECT tblCustomers.customerID AS customerID, firstname, lastname, vat,email
FROM tblCustomers
INNER JOIN tblContact on tblCustomers.customerID = tblContact.contactID
(or pick that other tables's column with the same if you need that one...)
And, frankly, I doubt your ON clause is the one you want to use. Shouldn't that be ON tblCustomers.customerID = tblContact.customerID instead?