Issue type:

[ ] question
[x] bug report
[ ] feature request
[ ] documentation issue

Database system/driver:

[ ] cordova
[ ] mongodb
[x] mssql
[x] mysql / mariadb
[ ] oracle
[ ] postgres
[ ] sqlite
[ ] sqljs
[ ] react-native

TypeORM version:

[x] latest
[ ] @next
[ ] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:

I have two tables:

product

id

product_attachment

id
product_id

var productAttachment = repository.findAndCount({ relations: 'product'});

QueryFailedError: ER_DUP_FIELDNAME: Duplicate column name 'ProductAttachment_product_id'

This issue happens because query builder generate alias ProductAttachment_product_id twice:
product_attachment.product_id -> ProductAttachment_product_id
product_attachment.product.id -> ProductAttachment_product_id