Database Interview Questions: What To Expect

If you are applying for a career involving databases – whether you want to be an engineer, an administrator, or a warehousing professional – you will need to show off your knowledge of both database lingo and function.

There is no excuse not to study for the inevitable interview questions, so let’s go over some of the questions you can expect to be asked and some good answers for them.  We’ll begin with the basics, and move on to some more specific questions.

The Basics

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 activity, the 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.