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What is database:
database is a storage system taht has a collection of data.

Types of database:
2 types :
1RBBMS:-relational database store in form of tables, that can easily retrived, managed,and update.
2.Non-RDBMS:-non relational database store data in the form document,graph.


What is Sql:-
sql is relational databse.
sql structured query language:
sql is a language to communicate with database.
sql command help you to store ,process ,analyze and manipulate database.



What is difference between sql and Nosql
sql: 1 sql  is relational database
     2.data store in tables
     3.databases have fixed or static or predefine schema.
     4.low performance with huge volumes of data.
     5.ex:-mysql,db2 , oracle,sql-server. 


nosql: 1. it is non relational database.
       2. data store in the key:value, document,graph.
       3. they have dynamic schema.
       4. Easily works with huge volumes of data
       5. exa:mongodb

Sql application:
CURD:- create, update,read ,delete

4 types of sql commands:
1.Data Defination language:DDL
   create,alter,Drop,Truncate.

2. Data manipulation language:DML
    select , insert,Update,delete

3. Data control language: DCL
   grant, revoke

4. Trasaction control language:TCL
    commit, rollback


Data Types:
Datatypes of a column defines what value the column can store in table.
Data type mailty classified into three categories:
1. numeric datatype:int ,float,bool, bigint,double.
2.string datatype: char, varchar
3.date &time: date,datetime,timestamp.
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Difference between char and varchar datatype:
char: 1.char datypes is use for store chracter string of fixed length.
      2.better performance than varchar


varchar:1.varchar datype is used to store character string of variable length.
        2. low performance  than char

comments in sql:-
single line comments:
-- this is sigle line comment 

multiline comments:-
/*  this is
multiline comment */
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create database:
syntax:-
create database database_name;

for checking database:
command: show databases;
for work database
command- use dattabase_name 

exa:
create database testdb;
use testdb;

show databases;

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create table:
syntax:
create table table_name(
     column1 datatype,
     column2 datatype,
     -
     -
     column3 datatype
   );

exa;
show tables;  --table check
create table Employee(
    empid int,
    name varchar(30),
    salary int,
    dept varchar(20),
    gender char(2)

);
desc Employee; - table describe

-- syntax:-create table tablename(colum1 datatype,column2 datatype,..........)
create table employee(emp_id int ,emp_name varchar(22) ,salary int ,city varchar(20),dept varchar(20));

-- 1.insert into tablename(columns) values()
-- 2. insert  into tablename values()
-- multiple insert value at one times
-- 3. insert into tablename values(  ...),(....),....alter
insert into employee(emp_name,emp_id,city,dept) values("pranita",1,"pune","IT");
insert into employee values(2,"akash",20000,"nashik","HR");

insert into employee(emp_name,emp_id,city,dept) values("pranita",1,"pune","IT"),("suyash",3,"Pune","IT"),("pavan",4,"nanded","IT");

insert into employee values(2,"akash",20000,"nashik","HR"),(5,"pavan",30000,"nanded","IT");

insert into employee values(1,"suhash",NULL,"pune","HR")


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