MySQL LIMIT结果与INNER JOIN有超过2个表

Question

I have a database where a user is allowed to have more than one email address. I want to query the database to get all the instances of a job for that customer. Each job is returning twice, one with each email.

Here is my query:

SELECT customers.first_name, customers.last_name, emails.email, services.title, services.description, jobs.status, jobs.job_id 
FROM customers 

INNER JOIN emails ON customers.user_id=emails.user_id 
INNER JOIN jobs ON customers.user_id=jobs.customer_id 
INNER JOIN services ON jobs.service_id=services.service_id;

It is returning something like this:

I want to return results with the first email only. The row should not be duplicated for each email address the user has on file.

How can this be done?

Answer 1

You can use GROUP BY on SQL to get unique column value like follows.

SELECT customers.first_name, customers.last_name, emails.email, services.title, services.description, jobs.status 
FROM customers 

INNER JOIN emails ON customers.user_id=emails.user_id 
INNER JOIN jobs ON customers.user_id=jobs.customer_id 
INNER JOIN services ON jobs.service_id=services.service_id;

GROUP BY jobs.job_id;