A Database is computing system that collects and stores data in an organized and structured manner. A database is managed by Database Management System (DBMS). Applications use database to store and access data.
Databases evolved from flat and hierarchical files during 1960s. Flat Database were simple flat like spreadsheet databases that were not structured which had columns and rows to store the data.
Hierarchical Databases were tree-like structured databases that was developed by IBM in the 1960s and used for their mainframe systems. They had records which is a collection of multiple data elements called fields of multiple types. In Hierarchical Database, a record will have links to another record below. The top record will be parent record and then below will be child record. The chain of hierarchy keeps growing down with the parent and child relationship. In Hierarchical Databases, each child record can only have one parent.
Network Database developed by Computer Scientist and Researcher Charles Bachman is a network-based database model that allowed records to have multiple parents and Childs (many-to-many relationship).
Relational Database was invented by Computer Scientist E. F. Codd during his time at IBM in 1970 using Relational model that organizes data into tables (relations) structurally in rows (tuples) which is the record and columns (attributes) that defines the property and characteristics of the data. Relational databases use keys to establish relationships between tables and ensure data integrity. The Primary Key uniquely identifies each row (record) within a table and Foreign Key is a field in the in a record that refers to a primary key in another table which creates a link between the tables. Relationship exists between tables which makes it a relationship data. Relational Database Management System (RDMS) is used manage Relational Databases. Structured query language (SQL) is a programming language for storing and processing information used by RDMS to manage relational database. Database schema is the structure of data that is used in RDBMS.
During 2000s Non-Relational Database also known as NoSQL Database stores data in a format unlike traditional table in a flexible data model using key-value pairs, graphs, documents and wide-columns. NoSQL Database are very scalable. They are suitable to store unstructured data. And also they don’t require fixed schema.
Big Data refers to data sets that are massive and complex data (structured, unstructured) to be handled and processed by traditional databases and other data processing tools. As the Internet grows exponentially, Big Data is growing along with it to handle and process large and complex data for benefiting organizations and people by analyzing and providing deep insights, patterns, trends to solve complex problems.