Попробуйте использовать REPLACE
функцию:
CREATE TABLE #Test(
Airports varchar(256),
id int
)
INSERT #Test(Airports,id)VALUES('dxb,cok,kwi',1)
INSERT #Test(Airports,id)VALUES('cok,dxb',2)
INSERT #Test(Airports,id)VALUES('kwi,dxb',3)
INSERT #Test(Airports,id)VALUES('kwi,dxb,zxc',4)
INSERT #Test(Airports,id)VALUES('dxb',5)
INSERT #Test(Airports,id)VALUES('aaa,bbb',6)
SELECT *,REPLACE(REPLACE(REPLACE(Airports,'dxb,',''),',dxb',''),'dxb','')
FROM #Test
UPDATE #Test
SET
Airports=REPLACE(REPLACE(REPLACE(Airports,'dxb,',''),',dxb',''),'dxb','')
WHERE Airports LIKE '%dxb%'
SELECT *
FROM #Test
DROP TABLE #Test