MySQL Workbench reports "is not valid at this position for this server version" error

Have you tried to run the query deleting the space between "COUNT" and the bracket? I run a similar query to yours on MYSQL 5.7 and it gives me an error, but without that space the query runs.

Let's try this:

SELECT COUNT(DISTINCT first_name) FROM actor;

I know this isn't the exact problem you stated, but this was the same error message I was getting. The message is so generic that it could be anything...

So, from one newbie to another:

For me, the error occurred when I nested one query within another. I had a ; at the end of the first query and forgot to take it out. That threw the error. Once I deleted the ; in the inner query and added one at the end of the new query the error resolved.

Error:

Select
From (....
    Select
    From
    Where
    Group by
    Order ;     <== offending ;
) as ...
Where
Group by
Order

No Error:

Select
From (....
    Select
    From
    Where
    Group by
    Order
) as ...
Where
Group by
Order ;   <== correct placement

Mine error resolved using 'db_name.' with table although I have already executed use 'db_name' command;

select * FROM db_name.table_name;