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Databases

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Databases

I will start by saying that databases form the most important part of any computer system or organization. First you got to protect the data. It’s everything, and everything else is secondary.

All other subjects, OS, Data Structures deal with how to store the data (whether in Trees or Tries) and how to extract it (Pagination and memory management). Database management is undoubtedly a very important part of any computer system.

And this is the reason, why databases become one of the most sought after competencies to be looked for in candidates appearing for interviews.

Let’s just skip some basic bookish terminologies, (which I’m sure you don’t remember, and don’t want to remember either ;)) and try to figure out what to know about databases, which could help you, excel in an interview.

Some points to be remembered before we start:

  • The Relational Model organizes data in the form of independent tables (consisting of rows and columns) that are related to each other.
  • A table consists of a number of rows (records/tuples) and columns (attributes). Each record contains values for the attributes.
  • The degree of the table denotes the number of columns.
  • A domain in the relational model is said to be atomic is it consists of indivisible units. For example, name is not atomic since it can be divided into first name and last name.
  • E. F. Codd laid down 12 rules (known as Codd's 12 rules) that outline the minimum functionality of a RDBMS. An RDBMS must comply with at least 6 of the rules.
  • Super Key is a set of attributes that collectively identify an entity in an entity set. For example, the bank account number is a super key in the bank accounts table.
  • Candidate Key (also known as Primary Key) is the smallest subset of the super key for which there does not exist a proper subset that is a super key.
  • Out of the multiple candidate keys, only one is selected to be the primary key and the remaining are alternate keys.
  • foreign key is the primary key of a table that is placed into a related table to represent one-to-many relationship among these tables.

In the coming articles under this section we’re going to cover all sorts of topics about databases; be it the Normalization forms or the ODBC/JDBC protocols or specific topics on databases like MySQL or Oracle and database programming. So stay tuned!!

Image source: mikke.bestevest.org

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