Convert string to date in lookup

Dear all,
I’ve got column char(6) containing string ‘201508’ (postgresql) , I want this string displayed like ‘August 2015’ (in grid application). I put this sql syntax using SQLBuilder :
SELECT to_char(to_date(substring(mycolumn,5,2) || ’ ’ || substring(mycolumn,1,4), ‘MM YYYY’),‘MONTH YYYY’)
FROM “public”.summ_sample
It return ‘August 2015’ but when I put in sql box in lookup (grid lookup) and run it, it give me an error.
Is there any way to formatting string from ‘201508’ to ‘August 2015’ ?
TIA

Aah, I’ve got it,
Just add ‘(’ and ‘)’ between function to_char and to_date, and It works.
SELECT to_char((to_date((substring(mycolumn,5,2) || ’ ’ || substring(mycolumn,1,4)), ‘MM YYYY’)),‘MONTH YYYY’)
FROM “public”.summ_sample
Thanks