Chapter 3 Building Physical Diagrams
You can access index properties from a table property sheet:
| Property | Description |
|---|---|
| Name | The name of the item which should be clear and meaningful, and should convey the item's purpose to non-technical users |
| Code | The technical name of the item used for generating code or scripts, which may be abbreviated, and should not generally include spaces |
| Comment | Descriptive label for the index |
| Stereotype | Sub-classification used to extend the semantics of an object without changing its structure; it can be predefined or user-defined |
| Owner | Name of index owner. You choose an owner from a list of users, the index and table owners can be identical or different. An index can only have one owner at a time. This is normally the index creator |
| Table | Indicate table to index |
| Type | Proprietary index type (for Sybase IQ, and Oracle only) |
| Unique | Indicate whether an index is a unique index |
| Cluster | Indicate whether an index is a clustered index |
An index also includes the following properties:
| Property | Description |
|---|---|
| Columns | Columns associated with index. This includes column definition indicating the primary key, foreign key, or alternate key to index. The index is associated with the columns of the selected key |
| Options | Physical options for the index. These are DBMS specific |
| Rules | Business rules attached to the index |
The following index types exist:
| Type | Description |
|---|---|
| Bitmap | (Oracle) In a bitmap index, a bitmap for each key value is used instead of a list of row Ids |
| HG | (Sybase IQ) HighGroup indexes are used for GROUP BY, COUNT(DISTINCT) and SELECT DISTINCT statements when data has more than 1000 unique values |
| HNG | (Sybase IQ) HighNonGroup indexes make equality comparisons, SUM and AVG calculations very fast when data has more than 1000 unique values. Nonequality comparisons can also be done |
| LF | (Sybase IQ) LowFast indexes are used for columns that have a very low number of unique values. This index also facilitates join index processing. It is one of the two indexes allowed for columns used in join relationships |
| CMP | (Sybase IQ) Compare indexes are used for columns that store the binary comparison (<, >, or =) of any two distinct columns with identical data types, precision, and scale |
| WD | (Sybase IQ) Is used to index keywords by treating the contents of a CHAR or VARCHAR column as a delimited list |
Some DBMS allow you to define an index owner, either identical or different from the table owner. If the DBMS of the current model does not support index owners, the table owner will be automatically assigned to the index after switching to a DBMS that supports index owners.
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