1. Indexes and Views
Unit 7

2. Key Concepts Index structure Clustered vs. non-clustered indexes
Query optimization
Creating indexes
Selecting index columns
Index forms
Creating views
Using views
Updating through views

3. Data Storage
Introduction to SQL, Figure 20.1, pg. 580

4. Indexed Data
Introduction to SQL, Figure 20.2, pg. 582

5. Indexes Based on one or more columns.
Stored as physical database items.
When indexed table columns are updated, indexes must also be updated.
Unique indexes are used to force uniqueness on index columns.
Single-column index, each value must be unique
Multiple-column index, the combined column value for each row must be unique

6. Clustered and Non-Clustered Indexes
Table is physically sorted in index order
A table can have only one clustered index
Non-clustered index
Logically organizes data
Does NOT change the data's physical storage
A table can have multiple non-clustered indexes

7. CREATE INDEX
Introduction to SQL, Example 20.7 and 20.9 on pg.591

8. Index Columns Commonly used as selection criteria High cardinality
Enforced uniqueness
Foreign key constraints

9. Impact of Cardinality
Introduction to SQL, Figure 20.4, pg. 599

10. Processing Speed
Introduction to SQL, Figure 20.5, pg 600

11. Index Forms Multitable (join) index Selective index Hash index
Bitmap index

12. View Fundamentals Virtual representation of one or more tables.
Used like a table when retrieving data.
Specify the columns available to users or applications.
Hide secure columns from users or applications.
Can include computed columns.

13. Creating Views
Introduction to SQL, Examples 21.1 and 21.2, pg. 612

14. Update Restrictions SELECT statement cannot contain:
DISTINCT
Aggregate functions
GROUP BY
HAVING
ORDER BY
Computed (virtual) columns cannot be updated.