MySQL: GROUP_CONCAT with LEFT JOIN
I'm experiencing a problem with MySQL's "GROUP_CONCAT" function. I will illustrate my problem using a simple help desk database:
CREATE TABLE Tickets (
id INTEGER NOT NULL PRIMARY KEY,
requester_name VARCHAR(255) NOT NULL,
description TEXT NOT NULL);
CREATE TABLE Solutions (
id INTEGER NOT NULL PRIMARY KEY,
ticket_id INTEGER NOT NULL,
technician_name VARCHAR(255) NOT NULL,
solution TEXT NOT NULL,
FOREIGN KEY (ticket_id) REFERENCES Tickets.id);
INSERT INTO Tickets VALUES(1, 'John Doe', 'My computer is not booting.');
INSERT INTO Tickets VALUES(2, 'Jane Doe', 'My browser keeps crashing.');
INSERT INTO Solutions VALUES(1, 1, 'Technician A', 'I tried to solve this but was unable to. I will pass this on to Technician B since he is more experienced than I am.');
INSERT INTO Solutions VALUES(2, 1, 'Technician B', 'I reseated the RAM and that fixed the problem.');
INSERT INTO Solutions VALUES(3, 2, 'Technician A', 'I was unable to figure this out. I will again pass this on to Technician B.');
INSERT INTO Solutions VALUES(4, 2, 'Technician B', 'I re-installed the browser and that fixed the problem.');
Notice that this help desk database has two tickets, each with two solution entries. My goal is to use a SELECT statement to create a list of all of the tickets in the database with their corrosponding solution entries. This is the SELECT statement I'm using:
SELECT Tickets.*, GROUP_CONCAT(Solutions.solution) AS CombinedSolutions
FROM Tickets
LEFT JOIN Solutions ON Tickets.id = Solutions.ticket_id
ORDER BY Tickets.id;
The problem with the above SELECT statement is it's returning only one row:
id: 1
requester_name: John Doe
description: My computer is not booting.
CombinedSolutions: I tried to solve this but was unable to. I will pass this on to Technician B since he is more experienced than I am.,I reseated the RAM and that fixed the problem.,I was unable to figure this out. I will again pass this on to Technician B.,I re-installed the browser and that fixed the problem.
Notice that it's returning ticket 1's information with both ticket 1's and ticket 2's solution entries.
What am I doing wrong? Thanks!
Use:
SELECT t.*,
x.combinedsolutions
FROM TICKETS t
LEFT JOIN (SELECT s.ticket_id,
GROUP_CONCAT(s.soution) AS combinedsolutions
FROM SOLUTIONS s
GROUP BY s.ticket_id) x ON x.ticket_id = t.ticket_id
Alternate:
SELECT t.*,
(SELECT GROUP_CONCAT(s.soution)
FROM SOLUTIONS s
WHERE s.ticket_id = t.ticket_id) AS combinedsolutions
FROM TICKETS t
You just need to add a GROUP_BY :
SELECT Tickets.*, GROUP_CONCAT(Solutions.solution) AS CombinedSolutions FROM Tickets
LEFT JOIN Solutions ON Tickets.id = Solutions.ticket_id
GROUP_BY Tickets.id
ORDER BY Tickets.id;