Oracle Developer

Provide an additional level of table security, by restricting access to a predetermined set of rows and columns of a table. Hide data complexity. Simplify commands for the user. Present the data in a different perpecetive from that of the base table. Store complex queries.

A sequence generates a serial list of unique numbers for numerical columns of a databases tables.

A synonym is an alias for a table, view, sequence or program unit.

There are two types of Synonyms Private and Public.

A Private Synonyms can be accessed only by the owner.

A Public synonyms can be accessed by any user on the database.

Synonyms are used to :

Mask the real name and owner of an object. Provide public access to an object Provide location transparency for tables,views or program units of a remote database. Simplify the SQL statements for database users.

An Index is an optional structure associated with a table to have direct access to rows,which can be created to increase the performance of data retrieval. Index can be created on one or more columns of a table.

Indexes are automatically maintained and used by ORACLE. Changes to table data are automatically incorporated into all relevant indexes.

Clusters are groups of one or more tables physically stores together to share common columns and are often used together.

The related columns of the tables in a cluster is called the Cluster Key.

A Cluster with an index on the Cluster Key.

A row is stored in a hash cluster based on the result of applying a hash function to the row's cluster key value. All rows with the same hash key value are stores together on disk.

No Limit.

The condition must be a Boolean expression evaluated using the values in the row being inserted or updated and can't contain subqueries, sequence, the SYSDATE,UID,USER or USERENV SQL functions, or the pseudo columns LEVEL or ROWNUM.

If a foreign key reference a parent key of the same table is called self-referential integrity constraint.

In Circumstances, all of the data for a row in a table may not be able to fit in the same data block. When this occurs , the data for the row is stored in a chain of data block (one or more) reserved for that segment.

An Extent is a specific number of contiguous data blocks, obtained in a single allocation, used to store a specific type of information.

A segment is a set of extents allocated for a certain logical structure.

Data Segment, Index Segment, Rollback Segment and Temporary Segment.