# SQL, the Structured Query Language

As a developer, you will work with the database, most of them will be Relational database and some, well they won’t be( for that you will have to learn more about the NoSql \[not only SQL\]).

Structural Query Language by Charles Kasasira

A relational database is a database structured to recognize relations between stored items of information.

**So, What is SQL**

SQL (Structured Query Language) is a tool for interacting with Relational Database Management Systems(RDBMS). It is a reliable and efficient language used for communicating with the database.

some of the most common database servers include:

\- MySQL

\- Oracle

\- Ms Access

**Why bother with SQL**

\-allows us to manage(create, rename, delete) databases.

\-manage databases tables

–Large amount of data is retrieved quickly and efficiently.

\-perform operations like Insertion, deletion, manipulation of data

“ What about NoSQL?-conversation for later “.

**Database principles and use**

What is a good database!

A good database should be:

\-concurrent:Multiple users can safely read and edit database entries simultaneously.

\-reliable:Relational databases formalize and can enforce concepts of “tidy” data.

\-scalable:Very large tables can be read, searched, and merged quickly.

\[**Most used SQL commands**\](https://www.w3schools.com/sql/sql\_syntax.asp)

*   SELECT — extracts data from a database
*   UPDATE — updates data in a database
*   DELETE — deletes data from a database
*   INSERT INTO — inserts new data into a database
*   CREATE DATABASE — creates a new database
*   ALTER DATABASE — modifies a database
*   CREATE TABLE — creates a new table
*   ALTER TABLE — modifies a table
*   DROP TABLE — deletes a table
*   CREATE INDEX — creates an index (search key)
*   DROP INDEX — deletes an index

**CONSTRAINTS(limitations for the data)**

1.Not Null

2.unique

3.Primary key

4.Foreign key

5.Default

6.Check

7.Create Index

Check constraint

Create index

**SQL JOIN**

A **SQL Join** statement is used to combine data or rows from two or more tables based on a common field between them

Types of joins

\-inner join

\-full join

\-left join

\-right join

I will have to make a full article about the joins, inform me if you love it.