1. Putting it back together
Inner Joins
Putting it back together

2. Overview
Normalization is the process of splitting information into separate tables, but often we want to see and use the information together
Joins bring the information from separate tables back together for queries

3. Types of Joins There are several types of joins
Inner Joins
Outer Joins
Cross Joins
Full Joins
We are only going to worry about inner joins for now

4. Keywords
Inner joins introduce three new keywords
INNER
JOIN ON

5. A Simple Inner join
SELECT ArtistName, Track_Title FROM Artist a INNER JOIN Tracks t ON a.ArtistID=t.ArtistID
In the SELECT clause list all the fields you wish to see from all the tables.
Put one of the tables in the FROM Clause
Place the other table after the INNER JOIN Clause
In the ON clause you tell which field relates the tables (key and Foreign Key, though the order doesn’t matter)
Note the aliasing of the tables

6. Joining More than 2 Tables
SELECT ArtistName, Track_Title, Cd_Title
FROM Artists a
INNER JOIN Tracks t
ON a.ArtisitID=t.ArtistID
INNER JOIN Cds c
ON c.CD_ID = t.CD_ID
WHERE ArtistName=‘U2’

7. In Access
To do the previous join in Access you would need to nest the join statements.
The next slide shows how Access handles the inner join
It is often easier to use the alternative syntax (Last slide)

8. Access Inner Join SELECT ArtistName, CD_Title, Track_Title FROM CDs
INNER JOIN (Artists
INNER JOIN Tracks
ON Artists.ArtistID = Tracks.ArtistID) ON CDs.CD_ID = Tracks.CD_ID
WHERE (((ArtistName)="U2"));

9. An Alternate Way
SELECT ArtistName, Track_Title, Cd_Title
FROM Artists a, Tracks t, Cds c
WHERE a.ArtistID=t.ArtistID
AND c.CD_ID=t.CD_ID
AND ArtistName=‘U2’
This is an older way. It was the only way Oracle supported before 9i