A database is an organized collection of data, generally stored and accessed electronically from a computer system.
A database that is storing data in the form of various files
Relational databases:
A relational database is a collection of data items with predefinedrelationships between them. These items are organized as a set of tables with columns and rows. Tables are used to hold information about the objects to be represented in the database. Each column in a table holds a certain kind of data and a field stores the actual value of an attribute. The rows in the table represent a collection of related values of one object or entity. Each row in a table could be marked with a unique identifier called a primary key, and rows among multiple tables can be made related using foreign keys. This data can be accessed in many different ways without reorganizing the database tables themselves.
Non-relational databases:
A non-relational database is a database that does not use the tabular schema of rows and columns found in most traditional relational databases. Instead, non-relational databases use a storage model that is optimized for the specific requirements of the type of data being stored.
Non-relational databases are purpose built for specific data models and have flexible schema for building modern applications. Non-relational databases are widely recognized for their ease of development, functionality, and performance at scale. They use a variety of data models, including document, graph, key-value, in-memory, and search.
Database Management Systems:
A database management system (DBMS) is a software package designed to define, manipulate, retrieve and manage data in a database. A DBMS generally manipulates the data itself, the data format, field names, record structure and file structure.
Relational DBMS:
Relational DBMS (RDBMS) is a DBMS designed specifically for relational databases. A relational database refers to a database that stores data in a structured format, using rows and columns.
Popular RDBMS — MySQL, Microsoft SQL Server, Oracle Database, etc.
Non-relational DBMS:
Non-relational Database Management System is designed specifically for non-relational databases. Data may be stored as simple key/value pairs, as JSON documents, or as a graph consisting of edges and vertices.
Popular Non-relational DBMS — MongoDB, Cassandra, etc.
What is SQL?
SQL is an abbreviation for Structured Query Language, and pronounced either see-kwell or es-que-el.
SQL is a standardized query language for requesting information from a database. In other words, SQL is a standard language for storing, manipulating and retrieving data in relational databases.
Types of SQL commands:
Data Definition Language (DDL) — DDL actually consists of the SQL commands that can be used to define the database schema. It simply deals with descriptions of the database schema and is used to create and modify the structure of database objects in the database.
DDL is used to define the schema of the database. In other words, it is used to create and alter tables and define the parameters of each column inside the tables. It is also used to delete objects from the database. Also, used to rename an object existing in the database.
Popular DDL commands — CREATE, DROP, ALTER, TRUNCATE, RENAME
2. Data Querying Language (DQL) — DQL statements are used for performing queries on the data within schema objects. The purpose of DQL Command is to get some schema relation based on the query passed to it.
DQL is used to retrieve specific information from the tables within the database.
Popular DQL commands — SELECT
3. Data Manipulation Language(DML)— These SQL commands deal with the manipulation of data already present in the database. These commands are used to make changes in the existing database.
Popular DML commands — INSERT, UPDATE, DELETE
4. Data Control Language (DCL) — DCL includes commands which mainly deal with the rights, permissions and other controls of the database system.
Popular DCL commands — GRANT, REVOKE
5. Transaction Control Language (TCL) — TCL commands deal with the transaction within the database. TCL includes statements that are used to manage the changes that are made from DML statements.
Popular TCL commands — COMMIT, SAVEPOINT, ROLLBACK
Ex-Data Analyst for Intuilize and Alliant Infotech
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