How to prioritize in OR condition in SQL Server -

i have simple query want search value in column, , if no match found want discard condition , select random value column.

i have tried achieve using or condition, using case, no avail

select top 10 *  tblrfcworkload  (f1 ='mbb' or f1 = f1) 

in above query want result table have rows 'mbb', if 'mbb' not found give value instead of mbb. instead returns 2 rows mbb though there 10 matching rows

select top 10 * tblrfcworkload 1 = case when f1 = 'mbb' 1 else 1 end 

this query returns same result 1st query

if change

select top 10 * tblrfcworkload 1 = case when f1 = 'mbb' 1 else 0 end 

then rows having mbb value.

need similar thing between clause... search 1 range if no results found search second range... how do that???

i think want this:

select top 10 * tblrfcworkload order (case when f1 = 'mbb' 1 else 2 end); 

this prioritizes rows want, fetching top 10 'mbb', if available.