Well... better yes.
More understandable? Hrm. Hold that thought.
*wanders off to try to dissect this monster*
Okay, this is REALLY oddly put together, and I think I see what they were TRYING to do, but they whiffed the organization.
With my preferred indentiing:
FROM
T1
FULL OUTER JOIN
T2
FULL OUTER JOIN
T3
INNER JOIN
T4
ON T3.Col3 = T4.Col3
FULL OUTER JOIN
T5
ON T3.Col1 = T5.Col1
AND T3.Col2 = T5.Col2
FULL OUTER JOIN
T6
ON T3.Col1 = T6.Col1
AND T3.Col2 = T6.Col2
FULL OUTER JOIN
T7
ON T3.Col1 = T7.Col1
AND T3.Col2 = T7.Col2
FULL OUTER JOIN
T8
ON T3.Col1 = T8.Col1
AND T3.Col2 = T8.Col2
ON T2.Col1 = T3.Col1
AND T2.Col2 = T3.Col2
ON T1.Col1 = T3.Col1
AND T1.Col2 = T3.Col2
FULL OUTER JOIN
T9
ONT3.Col1 = T9.Col1
AND T3.Col2 = T9.Col2
FULL OUTER JOIN
T10
ONT3.Col2 = T10.Col2
AND T3.Col3 = T10.Col3
You'll notice this all starts with that random inner join deep in the structure. I just think the original author didn't back out of it quickly enough, as nothing else hooks off T4, and there's no other limiters in the inner component.
So, T1 FULL (T2 FULL ( T3 INNER T4)) FULL T5... is what this is doing. The INNER join controls the data allowed to the T2/T3 and T1/T3 connectors.
This would be more obviously written as follows:
FROM
T1
FULL OUTER JOIN
T2
FULL OUTER JOIN
T3
INNER JOIN
T4
ON T3.Col3 = T4.Col3
ON T2.Col1 = T3.Col1
AND T2.Col2 = T3.Col2
ON T1.Col1 = T3.Col1
AND T1.Col2 = T3.Col2
FULL OUTER JOIN
T5
ON T3.Col1 = T5.Col1
AND T3.Col2 = T5.Col2
FULL OUTER JOIN
T6
ON T3.Col1 = T6.Col1
AND T3.Col2 = T6.Col2
FULL OUTER JOIN
T7
ON T3.Col1 = T7.Col1
AND T3.Col2 = T7.Col2
FULL OUTER JOIN
T8
ON T3.Col1 = T8.Col1
AND T3.Col2 = T8.Col2
FULL OUTER JOIN
T9
ONT3.Col1 = T9.Col1
AND T3.Col2 = T9.Col2
FULL OUTER JOIN
T10
ONT3.Col2 = T10.Col2
AND T3.Col3 = T10.Col3
Edit: Sorry, there's also a much more obvious way to write this, because T1 and T2 don't do anything prior to the involvement of T3/4, so there's no point.
FROM
T3
JOIN
T4
ONT3.Col3 = T4.Col3
FULL OUTER JOIN
T1
ON T1.Col1 = T3.Col1
AND T1.Col2 = T3.Col2
FULL OUTER JOIN
T2
ON T2.Col1 = T3.Col1
AND T2.Col2 = T3.Col2
FULL OUTER JOIN
T5
ON T3.Col1 = T5.Col1
AND T3.Col2 = T5.Col2
FULL OUTER JOIN
T6
ON T3.Col1 = T6.Col1
AND T3.Col2 = T6.Col2
FULL OUTER JOIN
T7
ON T3.Col1 = T7.Col1
AND T3.Col2 = T7.Col2
FULL OUTER JOIN
T8
ON T3.Col1 = T8.Col1
AND T3.Col2 = T8.Col2
FULL OUTER JOIN
T9
ONT3.Col1 = T9.Col1
AND T3.Col2 = T9.Col2
FULL OUTER JOIN
T10
ONT3.Col2 = T10.Col2
AND T3.Col3 = T10.Col3
