Monday, 9 February 2015

Oracle Interview Questions and Answers on SQL Queries (Page 3)

Below are some important Oracle Developer interview questions which are asked in most MNC company interviews for beginners or professionals.

21. Explain What are the advantages of Views?
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.

22. What is Sequence?
A sequence generates a serial list of unique numbers for numerical columns of a databases tables.

23. Explain a Synonym?
A synonym is an alias for a table, view, sequence or program unit.

24. Explain What are the type of Synonyms?
There are two types of Synonyms Private and Public.

25. Explain a Private Synonyms?
A Private Synonyms can be accessed only by the owner.

26. What is a Public Synonyms?
A Public synonyms can be accessed by any user on the database.

27. Explain What are synonyms used for?
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.

28. Explain an Index?
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.

29. Explain How are Indexes Update?
Indexes are automatically maintained and used by ORACLE. Changes to table data are automatically incorporated into all relevant indexes.

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