sql query output using if statement or switch case

Suppose i run a query

select open_mode from v$database

if it returns READ WRITE, output should return OK

otherwise output should return NOT OK.

also

if i run a query for table-space size check

& output is less than 90 percent value, output should return OK otherwise NOT OK.

I hope this can be achieve using if statement or switch case in ORACLE SQL query or at .sh file (shell scripting) level.

Need your inputs ?

for customized oracle database health check up report purpose