Microsoft® SQL Server® 2008 T-SQL Fundamentals

Chapter 6. Set Operations

In this chapter:

The UNION Set Operation

The INTERSECT Set Operation

The EXCEPT Set Operation

Precedence

Circumventing Unsupported Logical Phases

Conclusion

Exercises

Solutions

Set operations are operations between two input sets—or more accurately, multisets—resulting from two input queries. Remember, a multiset is not a true set because it can contain duplicates. When I use the term multiset in this chapter, I’m referring to the intermediate result sets from two input queries that may contain duplicates. Although there are two multisets as inputs to a SQL set operation, the final output is still one result set that may also be a multiset.

T-SQL supports three set operations: UNION, INTERSECT, and EXCEPT. ...