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SQL Anywhere 12.0.0 » Context-Sensitive Help » SQL Anywhere plug-in help » Introduction to SQL Anywhere properties windows

 

Index Properties window: General tab

This tab has the following components:

  • Name   Shows the name of the index. You can edit this field.

  • Type   Shows the type of object. The object type can be foreign key index, primary key index, unique constraint index, or index.

  • Unique   Shows whether values in the index must be unique. See UNIQUE clause.

  • Nulls Distinct   Shows whether NULLS are considered to distinct in the index columns. This option only appears if the type is Index and the index is Unique.

    When set to Yes, NULLS are considered distinct. For each row, the set of indexed columns must be unique or contain a NULL in at least one column. For example, for a unique index on two character columns, the index entries ('a', NULL) and ('a', NULL) are each considered distinct.

    When set to No, NULLS are considered not distinct. For each row, the set of indexed columns must be unique regardless of the NULL values. For example, for a unique index on two character columns, the index entries ('a', NULL) and ('a', NULL) are considered not distinct; hence, the index will prohibit these two entries.

    See WITH NULLS NOT DISTINCT clause.

  • Table   Shows the name and owner of the table with which the index is associated. This only appears if the index is on a table.

  • Materialized view   Shows the name and owner of the materialized view with which the index is associated. This only appears if the index is on a materialized view.

  • Dbspace   Shows the database file, or dbspace, where the index is located. This only applies to indexes on base tables and materialized views.

  • Clustered   Shows whether this index is a clustered index. Clustered indexes are supported for SQL Anywhere databases that are version 8.0.2 and later.

    Clustered indexes in SQL Anywhere store the table rows in approximately the same order as they appear in the corresponding index. Using a clustered index can lead to performance benefits by reducing the number of times each page needs to be read into memory. Only one index on a table can be a clustered index.

    See Using clustered indexes.

    • Set Clustered Index Now   Opens the Set Clustered Index window where you can specify that this index is a clustered index.

  • Format   Indicates that the store type of index the table has is compressed B-tree.

  • Comment   Provides a place for you to type a text description of the index. For example, you could use this area to describe the index's purpose in the system.

 See also