Beginning SQL

If you take this further and join the current sets of data to yet another table, then the first two joins must
be enclosed in brackets. The following is the original join:
FROM (MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
Then add the join to the Category table. Note that the first join is enclosed in brackets:
FROM ((MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
INNER JOIN Category
ON Category.CategoryId = FavCategory.CategoryId)
Now you can add the third join:
FROM ((MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
INNER JOIN Category
ON Category.CategoryId = FavCategory.CategoryId)
INNER JOIN Films
ON Category.CategoryId = Films.CategoryId;
The full SQL is as follows:
SELECT MemberDetails.MemberId
FROM ((MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
INNER JOIN Category
ON Category.CategoryId = FavCategory.CategoryId)
INNER JOIN Films
ON Category.CategoryId = Films.CategoryId;
If you add a fourth join, you need to enclose the first three joins in brackets:
SELECT MemberDetails.MemberId
FROM (((MemberDetails INNER JOIN FavCategory
ON MemberDetails.MemberId = FavCategory.MemberId)
INNER JOIN Category
ON Category.CategoryId = FavCategory.CategoryId)
INNER JOIN Films
ON Category.CategoryId = Films.CategoryId)
INNER JOIN Attendance
ON MemberDetails.MemberId = Attendance.MemberId;
And so it would continue if you add a fifth join, a sixth join, and so on.
Extracting Information
None of this adding of brackets is necessary for the other database systems, so the extra brackets aren’t
included in every example; be sure to add them if you’re using Access.
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