MariaDB 10.6

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showing values tblstore
'ofm','qf','RCS','TFV','TH'

CREATE TABLE `TT` (
  `item` varchar(250) NOT NULL,
  `price` double(10,2) NOT NULL,
  `desc` varchar(250) DEFAULT NULL,
  `store` varchar(125) DEFAULT NULL,
  `purchased` date DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;

/*Data for the table `TT` */

insert  into `TT`(`item`,`price`,`desc`,`store`,`purchased`) values 
('MCCAIN BISTRO FRIES',6.29,'N/A','ofm','2022-05-04'),
('NAVEL ORANGES LARGE',2.27,'N/A','ofm','2022-05-04'),
('WASH PINK LADY APPLE',2.46,'0.560kg@$4.39/kg','ofm','2022-05-04'),
('SSI GOAT CHEESE GARLIC',13.99,'N/A','ofm','2022-05-04'),
('PC TMTS GRLIC OL',1.29,'','RCS','2022-05-04'),
('ROTEL ORG TOM',2.00,'','RCS','2022-05-04'),
('MUTTI CHPPD TOMA',4.19,'','RCS','2022-05-04'),
('NABOB GOLD COFFEE 915GR SPECIAL',14.99,'','qf','2022-05-04'),
('DL H&H Cream Lactose FRE',4.99,'N/A','TFV','2022-05-04'),
('Morning Glory Muffins ',1.49,'N/A','TFV','2022-05-04'),
('Tomato Vine',4.32,'0.655 kg @ $6.59 / kg','TH','2022-05-15'),
('Coleslaw',2.69,'','TH','2022-05-15'),
('Bananas',2.37,'1.360 kg @ $1.74 / kg','TH','2022-05-15'),
('Mushroom Org White',2.31,'0.210 kg @ $11.00 / kg','TH','2022-05-15'),
('Grn Pepper',1.71,'0.210 kg @ $8313 / kg','TH','2022-05-15'),
('Onions Yellow Small',1.67,'0.380 kg @ $4.39 / kg','TH','2022-05-15'),
('Pork Loin Back Ribs',20.69,'','TH','2022-05-15'),
('Rouladen',13.63,'','TH','2022-05-15'),
('Muffin Bulk',3.98,'2@$1.99','TH','2022-05-15');

SELECT (GROUP_CONCAT(DISTINCT(CONCAT('''',store, '''' )))) AS 'showing values TT' FROM TT;

SELECT item, MAX(CASE WHEN store NOT IN ('ofm','qf','RCS','TFV','TH'  ) THEN price END) "other" FROM TT GROUP BY item;

SELECT item, MAX(CASE WHEN store NOT IN (TRIM((SELECT GROUP_CONCAT(CONCAT('''',store, '''' )) FROM tblstore))) THEN price END) "other" 
FROM TT GROUP BY item;

showing values TT
'ofm','qf','RCS','TFV','TH'

item	other
Bananas	null
Coleslaw	null
DL H&H Cream Lactose FRE	null
Grn Pepper	null
MCCAIN BISTRO FRIES	null
Morning Glory Muffins	null
Muffin Bulk	null
Mushroom Org White	null
MUTTI CHPPD TOMA	null
NABOB GOLD COFFEE 915GR SPECIAL	null
NAVEL ORANGES LARGE	null
Onions Yellow Small	null
PC TMTS GRLIC OL	null
Pork Loin Back Ribs	null
ROTEL ORG TOM	null
Rouladen	null
SSI GOAT CHEESE GARLIC	null
Tomato Vine	null
WASH PINK LADY APPLE	null

item	other
Bananas	2.37
Coleslaw	2.69
DL H&H Cream Lactose FRE	4.99
Grn Pepper	1.71
MCCAIN BISTRO FRIES	6.29
Morning Glory Muffins	1.49
Muffin Bulk	3.98
Mushroom Org White	2.31
MUTTI CHPPD TOMA	4.19
NABOB GOLD COFFEE 915GR SPECIAL	14.99
NAVEL ORANGES LARGE	2.27
Onions Yellow Small	1.67
PC TMTS GRLIC OL	1.29
Pork Loin Back Ribs	20.69
ROTEL ORG TOM	2.00
Rouladen	13.63
SSI GOAT CHEESE GARLIC	13.99
Tomato Vine	4.32
WASH PINK LADY APPLE	2.46