in topic you have specified select 'x'

so i think you wanted to know for select 'x' from tablename

the above query will return char x for all the records in the table.

normally stmts like these are used with exists/not exists

so instead of fetching all the columns in case where you want weather the data exists or not ,,simply use something like 'x',1 ,,

this will reduce the traffic and use less memory.