Whilst not offering any new functionality, they do allow simplicity in writing TSQL code.
The EXCEPT operator can be used to return records in one table and not in another (much like an outer join with an IS NULL WHERE clause)
The INTERCEPT operator will return the overlapping rows from two tables.
Both these commands operator in the same manor as a UNION clause.
Below is an example of using the EXCLUDE statement:
SELECT contestId
FROM Contest
EXCEPT
SELECT contestId
FROM PlayerContest
--(30%)
SELECT contestId
FROM Contest C
WHERE NOT EXISTS (SELECT 1 FROM PlayerContest PC WHERE C.contestId = PC.contestId)
--(30%)
SELECT C.contestId
FROM Contest C
LEFT JOIN PlayerContest PC
ON C.contestId = PC.contestId
WHERE PC.contestId IS NULL
--(40%)
All statements return exactly the same results, though in terms of performance, the first two are more efficient than the last one. The relative percentage cost is shown in brackets after each statement.
The INTERCEPT statement works in much the same way, and full details of both operators can be found in BOL.