What is SQL? Rules for using SQL | and Different SQL commands |Features of SQL by Anshul 2023

What is SQL?

SQL is short for Structured Query Language, and is pronounced S-Q-L or sometimes See-Quell. This database language is primarily designed for maintaining data in relational database management systems. It is a specialized tool used by data professionals to handle structured data (data that is stored in the form of tables). It is also designed for stream processing in RDSMS.

Features of SQL

SQL can be used by a wide range of users, including those with little programming experience.
SQL is a non-procedural language.
We can create and alter databases in SQL without any difficulty. This is not a time consuming process.
There is no persistence man in SQL anymore.
SQL is entered into the SQL buffer on one or more lines.
SQL uses a termination individual to execute instructions immediately. It uses features to do some formatting.
It uses functions to do some formatting.

SQL Usage

Data Definition: It is used to define the structure and organization of the stored data and the relationships between the stored data items.

Data Recovery: SQL can also be used for data recovery.

Data Manipulation: SQL also provides this facility if the user wants to add new data, delete data or modify existing data.

Access Control: SQL can be used to protect stored data from unauthorized access, restricting a user's ability to retrieve, add, and modify data.

Data sharing: SQL is used to coordinate data sharing by concurrent users, ensuring that changes made by one user do not inadvertently wipe out changes made by another user at approximately the same time.

Rules for SQL

';' to end SQL statements is used.
Statements can be split across lines, but keywords cannot.
Identifiers, operator names, and letters are separated by one or more spaces or other delimiters.
A comma (,) separates parameters without a clause.
A space separates a section.
Reserved words cannot be used as identifiers unless they are enclosed in double quotes.
Identifiers can be up to 30 characters long.
Identifiers must begin with an alphabetic character.
Characters and date characters must be enclosed within single quotation marks.
Numeric literals can be represented by simple values.
Comments may be enclosed between /* and */ symbols and may be multi-line.

How do SQL commands work?

Developers use Structured Query Language (SQL) commands, which are specific keywords or SQL statements, to work with data stored in relational databases. The following are the categories for SQL commands.

Data Definition Language (DDL)
Data Query Language (DQL)
Data Manipulation Language (DML)
Data Control Language (DCL)
Transaction Control Language (TCL)

Data Definition Language (DDL): The SQL commands used to create the database structure are known as Data Definition Language (DDL). Based on business needs, database engineers create and modify database objects using DDL. For example, the Create command is used by a database engineer to create database objects such as tables, views, and indexes.

Data Query Language (DQL): Data retrieval instructions are written in the Data Query Language (DQL), which is used to access relational databases. The SELECT command is used by software programs to filter and return particular results from an SQL table.

Data Manipulation Language (DML): A relational database can be updated with new data using Data Manipulation Language (DML) statements. For example, the INSERT command is used by an application to add a new record to a database.

Data Control Language (DCL): Data Control Language (DCL) is a programming language used by database administrators to provide or control access to a database to other users. For example, they may allow a specific application to manipulate one or more tables using the GRANT command.

Transaction Control Language (TCL): To automatically update the database, the relational engine uses the Transaction Control Language (TCL). For example, a database can reverse erroneous transactions using the ROLLBACK command.