Beginning SQL

Chapter 3
This time, you achieve more specific results:
FirstName LastName Category FilmName YearReleased
Jamie Hills War The Dirty Half Dozen 1987
Jamie Hills War Planet of the Japes 1967
Jamie Hills Horror The Lion, the Witch, and 1977
the Chest of Drawers
Jamie Hills Horror Nightmare on Oak Street, Part 23 1997
Jamie Hills Horror One Flew over the Crow’s Nest 1975
Jamie Hills Sci-fi The Wide Brimmed Hat 2005
Jamie Hills Sci-fi Soylent Yellow 1967
As you created the query, you probably noticed that each time you ran the query it produced a unique
set of results. That happens because each additional INNER JOIN linked to the results set created by the
previous SQL. Before moving on to the section that explains the set-based nature of SQL, you should
gain more familiarity with the use of brackets in MS Access.
Using Brackets around Inner Joins in MS Access
100
You can skip over this section if you’re not using MS Access. As mentioned previously, MS Access
requires brackets around joins when there’s more than one join. Each join creates a set of data, which is
discussed later. Each set of data needs to be enclosed in brackets, unless there’s only one set.
For example, the following statement involves only one join and therefore only one source set of data:
SELECT MemberDetails.MemberId
FROM MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId;
However, if you then join that set of data to another table, creating a second set of data, you must
enclose the first set of data inside brackets, like so:
SELECT MemberDetails.MemberId
FROM (MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
INNER JOIN Category
ON Category.CategoryId = FavCategory.CategoryId;
The following excerpt illustrates how the original join is enclosed inside its own brackets:
FROM (MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)