How to concatenate column values aggregated out of a group by? - mysql

Question

I have this MySQL query that works almost perfectly:
select ConfirmationNumber, ReservationDate, ifnull(CASE TableNumber WHEN 0 THEN 'UNASSIGNED' ELSE TableNumber END,'UNASSIGNED') AS 'Table', CONCAT(LastName, ', ', FirstName) AS 'Customer', Email, Phone, PublicNotes, sum(SleighSeats) + sum(CabSeats) AS Seats
from Reservations
where ReservationDate = '2018-1-25'
and ConfirmationNumber IS NOT NULL
and CancelDate IS NULL
group by TableNumber, Customer
order by TableNumber
It produces this result:
Focus on customer Corbosie... above.
Because there is grouping going on, there are PublicNotes data that I'm missing, because some records are being compressed out of the query. I simply want to concatenate the PublicNotes from all records included in the query, including those being aggregated out.
For example, when I query this way:
select ConfirmationNumber, ReservationDate, ifnull(CASE TableNumber WHEN 0 THEN 'UNASSIGNED' ELSE TableNumber END,'UNASSIGNED') AS 'Table', CONCAT(LastName, ', ', FirstName) AS 'Customer', Email, Phone, PublicNotes, SleighSeats + CabSeats AS Seats
from Reservations
where ConfirmationNumber in ('092550', '764352', '661800')
...it shows you 3 records that got compressed into 1 record (due to grouping) in the first query:
The 2 PublicNotes circled in red are missing because they got aggregated out. How can I maintain the grouping of my first query, while concatenating in the missing PublicNotes with their grouped record?

Answer 1

I think you want group_concat():
select ConfirmationNumber, ReservationDate,
(CASE TableNumber WHEN 0 THEN 'UNASSIGNED' ELSE TableNumber END) AS "Table",
CONCAT(LastName, ', ', FirstName) AS Customer,
Email, Phone,
GROUP_CONCAT(PublicNotes, '|'),
(SUM(SleighSeats) + SUM(CabSeats)) AS Seats
from Reservations
where ReservationDate = '2018-1-25' and
ConfirmationNumber IS NOT NULL and
CancelDate IS NULL
group by ConfirmationNumber, ReservationDate, TableNumber, Customer, email, phone
order by TableNumber;
Notes:
I don't think TableNumber can be NULL, based on the logic, so I removed the IFNULL(). If it can be, then add it back in (or use COALESCE().
I added the additional unaggregated columns to the GROUP BY. This is a good habit for you to use.
The separator for the different notes is a vertical bar. You can choose whatever you like.