MYSQL CASE THEN statement with multiple values

Question

I am trying go select multiple values with CASE statement. I noticed we cannot do

CASE 
    WHEN wall.type=\"bk\" 
    THEN books.id1,books.id2, //         


        

Answer 1

And everything can be done, but it always depends on what you want to do. Below I'll show you a working example right after you have to take the data as an array and do what you want.

CREATE TABLE wall (`ident` int,`type` varchar(2), `order` int);
INSERT INTO wall (`ident`, `type`, `order`) VALUES
    (40,'bk', 1),
    (41,'bk', 5),
    (42,'rt', 2),
    (43,'bk', 3),
    (44,'rt', 1);

CREATE TABLE books (`ident` int,`id1` int, `time` varchar(8), `id2` int);
INSERT INTO books (`ident`, `id1`, `time`, `id2`) VALUES
    (40, 10, '18:07:00', 20),
    (43, 11, '05:00:00', 21),
    (44, 12, '21:01:00', 22),
    (41, 13, '10:00:00', 23),
    (42, 14, '23:10:00', 24);
#--------------------------
SELECT 
  CASE 
    WHEN wall.type='bk' 
    THEN  CONCAT(books.id1,'-',books.id2) 
 END AS column_1

FROM wall JOIN books ON books.ident = wall.ident GROUP BY wall.ident ORDER BY wall.ident ASC;

Print:

 column_1
1   10-20
2   13-23
3   NULL
4   11-21
5   NULL

Solution in action via this link: http://rextester.com/LHPI38373