What is SQL ? SQL (Structured Query Language) is a programming language used for managing and manipulating relational databases. It can be used to insert, update, and retrieve data from a database, as well as to create and modify the structure of a database. Some of the common operations that can be performed using SQL include selecting data from tables, inserting new data into tables, updating existing data, and deleting data. It is a standard language for Relational Database Management Systems (RDBMS) such as MySQL, PostgreSQL, Microsoft SQL Server, Oracle, and many others. What is SQL ?
Before we continue with SQL, We should know about DATABASE.
What is DATABASE ? What is SQL ?
A database is a collection of data that is organized in a specific way and stored electronically. The purpose of a database is to enable efficient storage, retrieval, and manipulation of data. Databases are used in a wide range of applications, including online shopping, banking, and social media, as well as in business and scientific research.
There are several types of databases, including:
- Relational databases: The most common type of database, which stores data in tables with rows and columns. Each row represents a single record, and each column represents a field of data.
- Document databases: These databases store data in the form of documents, such as JSON or XML. Each document represents a single record, and each field within the document represents a piece of data.
- Key-value databases: These databases store data as a collection of key-value pairs. Each key represents a unique identifier for a piece of data, and the corresponding value is the data itself.
- Graph databases: These databases store data in the form of nodes and edges, which represent entities and their relationships. They are used for storing and querying data with complex relationships.
- Time-series databases: These databases are optimized for storing, querying and analyzing time-stamped data.
- Columnar databases: These databases store data in columns instead of rows. This allows for faster querying and aggregation of data on a specific column.
- Object-oriented databases: These databases store data in the form of objects, which are instances of classes.
Purpose of SQL
The purpose of SQL (Structured Query Language) is to manage and manipulate data in relational databases. SQL is used to insert, update, and retrieve data from a database, as well as to create and modify the structure of a database. Some of the main features and capabilities of SQL include:
- Data Definition Language (DDL): SQL includes commands for creating and modifying the structure of a database, such as creating tables, adding columns, and setting primary keys.
- Data Manipulation Language (DML): SQL includes commands for inserting, updating, and deleting data in a database, such as SELECT, INSERT, UPDATE, and DELETE.
- Data Control Language (DCL): SQL includes commands for controlling access to the data in a database, such as GRANT and REVOKE.
- Data Query Language (DQL): SQL includes commands for retrieving data from a database, such as SELECT, which is used to retrieve specific data from one or more tables.
- Data Aggregation: SQL includes commands for computing the aggregate values of data in a database, such as COUNT, SUM, AVG, MIN, and MAX.
- Data Joining: SQL includes commands for joining data from multiple tables together, such as JOIN, which is used to retrieve data from multiple tables in a single query.
- Data Constraints: SQL includes commands for setting constraints on the data in a database, such as NOT NULL and UNIQUE, which are used to ensure data integrity and consistency.
- Data Transactions: SQL includes commands for handling transactions, such as COMMIT and ROLLBACK, which are used to make sure data is consistent across multiple statements.
- Data indexing: SQL includes commands for indexing data, which is used to improve the performance of the queries.
SQL is a standard language and it’s widely used in most of the RDBMS(Relational Database Management Systems) like MySQL, Oracle, MS SQL Server, PostgreSQL and many more.
Here is a table that summarizes the main differences between SQL, MySQL, and NoSQL:
| Feature | SQL | MySQL | NoSQL |
|---|---|---|---|
| Data Model | Relational | Relational | Non-relational (e.g. document, key-value, graph) |
| Schema | Fixed and predefined | Fixed and predefined | Dynamic and flexible |
| Data Consistency | Strong consistency | Strong consistency | Eventual consistency |
| Data Relationships | Uses tables and foreign keys | Uses tables and foreign keys | Uses embedded documents or references |
| Query Language | SQL (Structured Query Language) | SQL (Structured Query Language) | Various (e.g. MongoDB uses its own query language) |
| Strong consistency | Typically achieved through replication and sharding | Typically achieved through replication and sharding | Typically achieved through horizontal scaling and distributed architectures |
SQL is a standard language for RDBMS and MySQL is one of the widely used RDBMS which uses SQL, NoSQL is non-relational databases and it’s not based on SQL language.
Differences between a DBMS (Database Management System) and an RDBMS (Relational Database Management System):
| Feature | DBMS | RDBMS |
|---|---|---|
| Data Model | Not limited to any specific data model | Relational |
| Data Integrity | Not necessary | Ensured by using primary key, foreign key and other integrity constraints |
| Data Access | Data may be accessed in a variety of ways | Data is accessed using SQL (Structured Query Language) |
| Data relationships | May not support relationships between data | Support relationships between data through the use of tables and foreign keys |
| Data Security | May not provide advanced security features | Provide advanced security features like user roles, access controls, and encryption |
In summary, DBMS is a general term that refers to any system that can be used to manage a database, while RDBMS is a specific type of DBMS that is based on the relational model and uses SQL to access and manipulate data. RDBMSs enforce data integrity and consistency through the use of constraints, and provide advanced security features. What is SQL ? What is SQL ? What is SQL ? What is SQL ?
What is SQL ? What is SQL ? What is SQL ? What is SQL ?