Beginning Microsoft SQL Server 2008 ... - S3 Tech Training

How It Works
As you can see, we have the same two rows that we would have had with an INNER JOIN clause. Those
are then followed by the three Address records that aren’t matched with anything in either table. Last,
but not least, we have the one record from the Vendors table that wasn’t matched with anything.
Again, use a FULL JOIN when you want all records from both sides of the JOIN — matched where possible,
but included even if there is no match.
CROSS JOINs
CROSS JOINs are very strange critters indeed. A CROSS JOIN differs from other JOINs in that there is no
ON operator and that it joins every record on one side of the JOIN with every record on the other side of
the JOIN. In short, you wind up with a Cartesian product of all the records on both sides of the JOIN.
The syntax is the same as any other JOIN, except that it uses the keyword CROSS (instead of INNER,
OUTER, or FULL) and that it has no ON operator. Here’s a quick example:
SELECT v.VendorName, a.Address
FROM Vendors v
CROSS JOIN Address a
Think back now — we had three records in the Vendors table and five records in the Address table. If
we’re going to match every record in the Vendors table with every record in the Address table, then we
should end up with 3 * 5 = 15 records in our CROSS JOIN:
VendorName Address
--------------------------- --------------------
Don’s Database Design Shop 1234 Anywhere
Don’s Database Design Shop 567 Main St.
Don’s Database Design Shop 999 1st St.
Don’s Database Design Shop 1212 Smith Ave
Don’s Database Design Shop 364 Westin
Dave’s Data 1234 Anywhere
Dave’s Data 567 Main St.
Dave’s Data 999 1st St.
Dave’s Data 1212 Smith Ave
Dave’s Data 364 Westin
The SQL Sequel 1234 Anywhere
The SQL Sequel 567 Main St.
The SQL Sequel 999 1st St.
The SQL Sequel 1212 Smith Ave
The SQL Sequel 364 Westin
(15 row(s) affected)
Indeed, that’s exactly what we get.
Chapter 4: JOINs
103