MySql Count cannot show 0 values

问题

I have two tables one Employee and mailing Subscriptions Employee looks like this:

Name (pk) | Surname | Age

mailing Subsriptions

MailId (pk)| EmployeeName (fk)|Description | Date

I wanted to subscription number for each customer, therefore I tried the following query:

Select COUNT(c.Name) 
From Employee 
    INNER JOIN mailingSubscriptions as m ON c.Name = m.EmployeeName;

It will give me all counts for each Employee that has an entry in the mailing subscription.

My problem is that I want to see the counts for ALL the Employees, including the ones without an entry (therefore to show 0), I tried an outer left/right join, but it will not work. Am I doing something wrong?

回答1:

SELECT c.name, count(m.mailid)
FROM Employee 
   LEFT JOIN mailingSubscriptions as m ON c.Name = m.EmployeeName
GROUP BY c.name;

来源：https://stackoverflow.com/questions/5448368/mysql-count-cannot-show-0-values