SQL EASILY EXPLAINED

 SQL EASILY EXPLAINED

Many if not all organizations have large amounts of data that need to be securely stored, updated and retrieved easily. Nowadays data is more valuable than oil if analyzed and interpreted properly.

Then what is data? in simple terms data are raw facts, example comments on a Facebook post.

In the Facebook comment example  the Facebook company must have a database that stores those comments. This brings us to the term database.

A database is easily defined as a container (think of a box) that stores data. A database can be relational and no relational. Relational database is the oldest form of a database as it was the first  and currently most commonly used.

Storing data in files can lead to redundancy, wastage of time and there is a possibility of having a hard time trying to retrieve files especially when looking for related information. Here is when DBMS come to our aid. What is DBMS? it is an acronym of database management system. DBMS is a generalized software that is used to manage databases. The software applications can be python, c++,JavaScript and even R.

SQL ,structured query language as the name suggests is used to query the databases is the standard  of querying the database. Most programmers use the standard in order to allow other people to read the queries easily and also allow for  understanding when updating.

The queries are usually written in capital letters and when ending a code, we use a semicolon .SQL is not case sensitive but we must maintain the heywell standards. Some SQL flavors are  mysql,oracle,posgresql,Microsoftsql server etc. the mentioned above are relational. The most common no relational database is mongo dB.

The major aims of querying a database is CRUD

C- create

R-read

U- update

D-delete.

Here I will give you some simple MySQL queries and some of the mostly used aggregate functions.

Let’s say provided the dataset below create a database called college?

Students table:

Students ID	Name	Age	Year of admission
1	Onunga	78	2017
2	Wanga	23	2016
3	Ogeto	39	2015
4	Malenya	56	2017

 

Course table:

Course ID	Course name	Students ID	Department
1	arts	4	Education
2	physics	3	Science
3	statistics	1	Mathematics
4	economics	2	Bussiness

 

 

 

CREATING A DATABASE

we use create query to create a database ie

CREATE DATABASE college;

Now that we have created  the database college lets create the tables and insert the provided data 

CREATE TABLE studentS (

id INT,

name VARCHAR(50),

year_adm INT,

age INT

);

CREATE TABLE Course(

course_id INT,

student_id INT,

department VARCHAR(200 )

) ;

Students id is an integer field ,students name is a character field and the set limit for cgaractors in this field is 50.

INSERTING THE DATA INTO THE TABLES

Here we shall use the query insert into

INSERT INTO  studentS(id,s_name,year_adm,age)

VALUES(1,'onunga',2017,78);

INSERT INTO  studentS(id,s_name,year_adm,age)

VALUES(2,'wanga',2016,23);

INSERT INTO  studentS(id,s_name,year_adm,age)

VALUES(3,'ogeto',2015,39);

INSERT INTO  studentS(id,s_name,year_adm,age)

VALUES(4,'malenya',2017,56);

INSERT INTO  Course (course_id,student_id,department)

VALUES(1,4,'Education');

INSERT INTO  Course (course_id,student_id,department)

VALUES(2,3,'Science');

INSERT INTO  Course (course_id,student_id,department)

VALUES(3,1,'Mathematics');

INSERT INTO  Course (course_id,student_id,department)

VALUES(4,2,'Bussiness');