I have 2 tables, one with functions and one with used functions. I have a query which only has to show me the values which are not used. So it has to compare if the function name exists in the other table, if not show that value.

For example this is my database table **functions**:

```
function_id | function_name | function_description
1           | function_1    | lorem ipsum
2           | function_2    | dolor sit amet

```

And this is my table **used functions**:

```
register_id | function_activation | function_deactivation | etc
1           | function_1          | function_1            | lorem ipsum

```

So like function\_2 does **not** exist in the **used functions** table. I used this query to check it:

```
SELECT * FROM functions WHERE NOT EXISTS 
 (SELECT function_activation, function_deactivation FROM used_functions)

```

But it shows me nothing. Am I using a wrong query or maybe something else?