Database Administration Interview Preparation Guide
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Database Administration guideline for job interview preparation. Explore list of Database Administration frequently asked questions(FAQs) asked in number of Database Administration interviews. Post your comments as your suggestions, questions and answers on any Database Administration Interview Question or answer. Ask Database Administration Question, your question will be answered by our fellow friends.

25 Database Administration Questions and Answers:

1 :: Explain database clusters?

Group of tables physically stored together because they share common columns and are often used together is called Cluster.
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2 :: Explain What is a lookup table in database? where can we use these type of table?

Lookup tables are like constraints which hold a value. The content in the lookup tables dosen't change often, hence refered as lookup (reference).

Example : Countries table

Countries are not added on regular bases hence one can consider the table as a lookup table. As and when needed in some other table the countries information can be fetched base on PK - Country-Code column. Eg - Emp_Per_Info.
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3 :: Explain Different types of table join?

different types of joins are

-Cartesian Product or Cross Join
-Inner Join
-Equi Join or Natural Join
-Non Equi Join
-Self Join
-Outer Join
-Left Outer Join
-Right Outer Join
-Full Outer Join
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4 :: Explain When can hash cluster used?

Hash clusters are useful in cases where :
(i) There is a uniform, even and predictable no. of key values.
(ii) Queries using equality predicates.
(iii) The table is NOT growing constantly, and the keys are rarely updated.
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5 :: Explain What is an Oracle sequence?

A sequence is a database object created by a user that can be used to generate unique integers. A typical usage of sequences is to generate primary key values which are unique for each row.
It is generated and incremented (or decremented) by an internal Oracle routine. It can be used by multiple users and for multiple tables too. A sequence can be used instead of writing an application code for sequence-generating routine.
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6 :: Explain What is an extent?

An Extent is a collection of contagious blocks the second level of granuality of the storage in database is called extent.it is defined as the collectionof contagious datablocks.
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7 :: Explain What is a cursor? Why do you need them? What are the different kinds of cursor?

oracle uses private sql area to execute sql queries and store the information.pl/sql uses cursors to name these private sql area and access its stored information
there r two types of cursors
implicit
explicit

implicit cursors are used for all dml and single row queries.these are system defined

explicit cursors are used for queries which return multiple row .these are user defined.
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8 :: Explain What is hash cluster?

This is an alternate to index, as index fast retrieve rows from single column,same way hash cluster fast retrieve rows from group of table and reduce i/o .
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9 :: Explain What is a tablespace?

An Oracle database consists of one or more logical storage units called tablespaces, which collectivley store all of the database's data.

Each tablespace in an ORACLE database consists of one or more files called datafiles, which are physical structures that conform with the operating system in which Oracle is running.

For Example::: A simple Oracle Database have one tablespace and one datafile.
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10 :: Explain What is index cluster?

An index cluster uses an index to maintain data within the cluster. The structure of a cluster index is similar to a normal index.
Although a normal index does not store NULL key values, and index cluster can store it.
And, a cluster index is likely to be smaller than a normal index because, there is only one entry for each key value in the cluster index, even if that is repeating.
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