Relational Database

A Relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by E. F. Codd.

Table

• The data in an RDBMS is stored in database objects which are called as tables.
• This table is basically a collection of related data entries and it consists of numerous columns and rows.
• A table is the most common and simplest form of data storage in a relational database.

What is a field?

A field is a column in a table that is designed to maintain specific information about every record in the table.

What is a Record or a Row?

A record is also called as a row of data is each individual entry that exists in a table.

What is a column?

A column is a vertical entity in a table that contains all information associated with a specific field in a table.

Primary key

A column that uniquely identifies the rows in a table can be called a primary key.

Indexing

Index drastically speeds up data retrieval An index or database index is a data structure which is used to quickly locate and access the data in a database table.

Indexes are created using some database columns.

The first column is the Search key that contains a copy of the primary key or candidate key of the table. These values are stored in sorted order so that the corresponding data can be accessed quickly (Note that the data may or may not be stored in sorted order). The second column is the Data Reference which contains a set of pointers holding the address of the disk block where that particular key value can be found.

ACID

ACID is a set of properties of relational database transactions.

Atomicity - Each transaction is all or nothing Consistency - Any transaction will bring the database from one valid state to another Isolation - Executing transactions concurrently has the same results as if the transactions were executed serially Durability - Once a transaction has been committed, it will remain so

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