I am attempting to retrieve either a null or boolean value from a query. Here is my query:

```
SELECT EXISTS (SELECT 1 FROM employee
               where add_uuid = '7e53fa47-ade3-4e94-8efd-b25f998b09c6') AS a,
       CASE WHEN a = false then null
            ELSE (SELECT exists (SELECT 1 FROM employee
                                 where add_uuid = '7e53fa47-ade3-4e94-8efd-b25f998b09c6'
                                 and is_active = true
                                )
                 )
       END 

```

Results in:

> 
> SQL Error [42703]: ERROR: column "a" does not exist
> 
> 
> 

Despite experimenting with multiple options, I am still unable to achieve the desired outcome.