Every organization has data that needs to be collected, managed, and analyzed. A relational database fulfills these needs. Along with the powerful features of a relational database come requirements for developing and maintaining the database. Data analysts, database designers, and database administrators (DBAs) need to be
able to translate the data in a database into useful information for both day-to-day operations and long-term planning.
The relational model is the basis for any relational database management system (RDBMS). A relational model has three core components: a collection of objects or relations, operators that act on the objects or relations, and data integrity methods. In other words, it has a place to store the data, a way to create and retrieve the data, and a way to make sure that the data is logically consistent.
Relational Database
A collection of tables that stores data without any assumptions as to how the data is related within the tables or between the tables.
Table
The basic construct of a relational database that contains rows and columns of related data.
Relation
A two-dimensional structure used to hold related information, also known as a table.
Row
A group of one or more data elements in a database table that describes a person, place, or thing.
Column
The component of a database table that contains all of the data of the same name and type across all rows.
Field
The smallest piece of information that can be retrieved by the database query language. A field is found at the intersection of a row and a column in a database table
Primary key
A column (or columns) in a table that makes the row in the table distinguishable from every other row in
the same table.
Foreign key
A column (or columns) in a table that draws its values from a primary or unique key column in another table. A foreign key assists in ensuring the data integrity of a table.
Referential integrity
A method employed by a relational database system that enforces one to-many relationships between tables.
Data modeling.
A process of defining the entities, attributes, and relationships between the entities in preparation for creating the physical database.
Relationship
1.One to One
2.One to Many
3.Many to Many
One-to-One relationship
A relationship type between tables where one row in a given table is related to only one or zero rows in a second table. This relationship type is often used for subtyping.
For example, an EMPLOYEE table may hold the information common to all employees, while the FULLTIME, PARTTIME, and CONTRACTOR tables hold information unique to full time employees, part time employees and contractors respectively. These entities would be considered subtypes of an EMPLOYEE and maintain a one-to-one relationship with the EMPLOYEE table.
Many-to-Many relationship
A relationship type between tables in a relational database where one row of a given table may be related to many rows of another table, and vice versa. Many-to many relationships are often resolved with an intermediate associative table.
