<p>Given a collection of user specified tags how do I determine which ones <strong>are not</strong> in the tags table with 1 SQL Statement?</p>

<p>Assuming a table schema <code>tags (id, tag)</code> and I'm using mysql, if there's an optimization I'm unaware of.</p>

<p>thanks</p>

```
```
select * from canonical_list_of_tags where tag not in (select tag from used_tags)
```
```
At least that works in T-SQL for SQL Server ...
Edit:
Assuming that the table
```
canonical_list_of_tags
```
is populated with the result of "
Given a collection of user specified tags
"