Monday, July 29, 2013

Database Interview Questions

Q:  What is data mining and how can it be used?
A:  Data mining refers to any procedure for collecting, analyzing, and summarizing the contents of a database.  It can be used to judge the success of a business, marketing campaigns, and to forecast future trends.

Q:  What is database normalization and why is it done?
A:   This is the process of organizing data in a database efficiently, and it is done to make sure that connections and dependencies between data make sense, and to get rid of redundant data.


Q:  What are fact tables?
A:  Tables which track the progress of a certain process or activitythe primary tables of databases.

Q:  What are attributes?
A:  An attribute is a column in a table.

Q:  What does SQL stand for, and what is it used for?
A:  SQL stands for structured query language, used with relational databases.  It is used to query, update, and retrieve the contents of databases.

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Q:  What does RDMBS stand for, and what does it do?
A:  Relational database management systems are the basis of SQL, and they are used to manage the database and intelligently store data in related rows and columns with identifiers and indexes.

Q:  What do constraints do?  What are the types of constraints?
A:  Constraints are used to prevent the database from losing internal and external integrity.  The types are: check, not null, unique, primary key, and foreign key.

Q:  Describe the difference between primary keys and foreign keys.
A:  Primary keys are at least one column in a table that identify specific rows in that same table.  Foreign keys are columns in a table that identify rows in a different table.

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Questions about MySQL

Q:  What are the commands to start and stop MySQL?
A:  -NET START MySQL and -NET STOP MySQL

Q:  What is the MySQL server default port?
A:  The default port is 3306.

Q:  What is the MySQL command to get a list of user accounts?
A:  -SELECT User FROM mysql.user

Q:  What is the MySQL command to concatenate a string of characters?
A:  -CONCAT(string1, string2, string3)

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Q:  What is the MySQL command to delete a column?
A:  -ALTER TABLE table_name DROP column_name

Questions about Oracle

Q:  What does each number in the version number of an Oracle release stand for?
A:  First number – major database release number.  Second – database maintenance release number.  Third – application server release number.  Fourth – component specific release number.  Fifth – platform specific release number.

Q:  What does concurrency refer to?
A:  Concurrency refers to when multiple different users can access the same data at the same time.

Q:  What Large object types are used in Oracle?
A:  The Clob and Blob object types are used.

Q:  What is BCP?
A:  BCP is the bulk copy tool, which allows you to quickly and easily import and export large amounts of data to and from tables.

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Q:  What is the difference between privileges and grants?
A:  Privileges are given to users and give them the right to execute certain commands, like the right to connect to a certain database.  Grants are given to particular objects by their owners, and allow them to be accessed in certain ways.

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