<t>As per the documentation: FROM (Transact-SQL):<br/>
<br/>
::= <br/>
[ { INNER | { { LEFT | RIGHT | FULL } [ OUTER ] } } [ ] ]<br/>
JOIN<br/>
<br/>
```<br/>
<br/>
The keyword `OUTER` is marked as optional (enclosed in square brackets). In this specific case, whether you specify `OUTER` or not makes no difference. Note that while the other elements of the join clause is also marked as optional, leaving *them* out *will* make a difference.<br/>
<br/>
For instance, the entire type-part of the `JOIN` clause is optional, in which case the default is `INNER` if you just specify `JOIN`. In other words, this is legal:<br/>
<br/>
```<br/>
SELECT *<br/>
FROM A JOIN B ON A.X = B.Y<br/>
<br/>
```<br/>
<br/>
Here's a list of equivalent syntaxes:<br/>
<br/>
```<br/>
A LEFT JOIN B A LEFT OUTER JOIN B<br/>
A RIGHT JOIN B A RIGHT OUTER JOIN B<br/>
A FULL JOIN B A FULL OUTER JOIN B<br/>
A INNER JOIN B A JOIN B<br/>
<br/>
```<br/>
<br/>
Also take a look at the answer I left on this other SO question: [SQL left join vs multiple tables on FROM line?](https://stackoverflow.com/a/894659/267).</t>
