Overview of SQL

SQL is a language for working with databases that includes many operations such as creating databases, deleting, extracting data, modifying data, etc. SQL has many versions.

SQL is a language for working with databases that includes many operations such as creating databases, deleting, extracting data, modifying data, etc. In this series of articles we will learn Learn basic knowledge of SQL, create tables, queries, clauses,. Remember to follow along.

What is SQL?

SQL , short for Structured Query Language , is a structured query language that allows you to access and manipulate databases to create, delete, modify, and extract data.

SQL is also the standard language for relational database systems. All database management systems (RDBMS) such as MySQL, MS Access, Oracle, Sybase, Informix, Postgres or SQL Server take SQL as the standard database language.

If you learn about Microsoft's SQL Server, you will know that in addition to SQL, this database system also uses T-SQL as a "local" language, Oracle SQL also uses PL/SQL,.

SQL has been around since 1970 when Dr. IBM's Edgar F. "Ted" Codd describes a relational model for databases. In 1974, SQL began to appear. Four years later, IBM developed Codd's ideas and created a product called System/R. In 1986, IBM developed the first prototype of a relational database, which was standardized by ANSI. The first relational database was released by Relational Software (which is now Oracle).

What can SQL do?

SQL offers many benefits, such as:

Execute queries against the database
Get data from database
Insert records into the database
Update records in the database
Delete records from the database
Create a new database
Create a new table in the database
Create stored procedures in the database
Create views in the database
Set permissions on tables, procedures, and views

How are SQL commands executed?

When you execute an SQL command on any relational database management system, the system decides the best way to execute that command, and the SQL engine helps you understand how the task is interpreted. any.

There are many components in this process: Query Dispatcher, Optimization Engines, Classic Query Engine, SQL Query Engine.

SQL commands

The following are some basic command groups (classified according to the nature of the command) of SQL:

DDL - Data Definition Language

CREATE: Create new tables, table views and other objects in the database.
ALTER: Edit existing data objects, such as tables.
DROP: Delete entire tables, table views or other objects in the database.

DML - Data Manipulation Language (Language for manipulating data)

SELECT: Extract specific records from one or more tables
INSERT: Insert new data into the database.
UPDATE: Modify and update data in the database.
DELETE: Delete data from the database.

DCL - Data Control Language

GRANT: Grant privileges to the user
REVOKE: Restore the permissions granted to the user

At this point, you have a brief understanding of SQL, basic SQL commands as well as the functions of those commands. In the next lesson, we will learn about RDBMS, data components in relational database systems,.