In MySQL, how to select empty records - php

Question

I have the following MySQL Table Structure:
mysql> desc customers;
+---------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+---------------------+-------------+------+-----+---------+-------+
| hash | varchar(32) | NO | PRI | NULL | |
| date_joined | date | NO | | NULL | |
| agent_code | int(5) | NO | UNI | | |
+---------------------+-------------+------+-----+---------+-------+
mysql> desc persons;
+--------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+-------------+------+-----+---------+-------+
| agent_code | int(5) | NO | UNI | | |
| team_id | int(2) | YES | | 0 | |
| hash | varchar(32) | NO | PRI | NULL | |
+--------------------+-------------+------+-----+---------+-------+
mysql> desc teams;
+--------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+-------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | YES | | NULL | |
| leader | varchar(32) | NO | UNI | NULL | |
+--------+-------------+------+-----+---------+----------------+
And I'd wish to generate a report of sales by Team.
The SQL Query that I'm using is the following:
SELECT COUNT(`customers`.`agent_code) AS `customer_count`, `teams`.`name`
FROM `customers`
JOIN `persons` ON `customers`.`agent_code` = `persons`.`agent_code`
JOIN `teams` ON `persons`.`team_id` = `teams`.`id`
GROUP BY `teams`.`name`
And it shows the following information:
+----------------+--------+
| customer_count | name |
+----------------+--------+
| 3 | Team 1 |
+----------------+--------+
However I'd like to see the "customer_count" of all the teams in the database, even if the customer_count is null (or zero) for a given team. I have 15 teams in my database, so I'd like to see something like:
+----------------+--------+
| customer_count | name |
+----------------+--------+
| 3 | Team 1 |
| 0 | Team 2 |
| 0 | Team 3 |
| 0 | Team 4 |
+----------------+--------+
I have tried to execute some variants of the following Query, but I always get an error saying that the syntax of OUTER JOIN is incorrect, even though I've read the documentation, and it is correct.
SELECT COUNT( `customers`.`agent_code` ) AS `customer_count` , `teams`.`name`
FROM `customers`
LEFT JOIN `persons` ON `customers`.`agent_code` = `persons`.`agent_code`
LEFT OUTER JOIN `teams` ON `persons`.`team_id` = `teams`.`id`
GROUP BY `teams`.`name`
How can I alter my current query in order to display such result?

Answer 1

You have mistake get main table is person - I suggest your main table is team
SELECT COUNT(`customers`.`id`) AS `customer_count` , `teams`.`name`
FROM `teams`
JOIN `persons` ON `persons`.`team_id` = `teams`.`id`
LEFT JOIN `customers` ON `customers`.`agent_code` = `persons`.`agent_code`
GROUP BY `teams`.`name`
Update: if you do have empty teams, than you need to set left join on persons
SELECT COUNT(`customers`.`id`) AS `customer_count` , `teams`.`name`
FROM `teams`
LEFT JOIN `persons` ON `persons`.`team_id` = `teams`.`id`
LEFT JOIN `customers` ON `customers`.`agent_code` = `persons`.`agent_code`
GROUP BY `teams`.`name`