SQL Queries

SQL


Introduction:

SQL is a standard language for accessing and manipulating databases.

What is SQL?• SQL stands for Structured Query Language
• SQL lets you access and manipulate databases
• SQL is an ANSI (American National Standards Institute) standard

What Can SQL do?• SQL can execute queries against a database
• SQL can retrieve data from a database
• SQL can insert records in a database
• SQL can update records in a database
• SQL can delete records from a database
• SQL can create new databases
• SQL can create new tables in a database
• SQL can create stored procedures in a database
• SQL can create views in a database
• SQL can set permissions on tables, procedures, and views

SQL DML and DDL
SQL can be divided into two parts: The Data Manipulation Language (DML) and the Data Definition Language (DDL).
The query and update commands form the DML part of SQL:
• 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
The DDL part of SQL permits database tables to be created or deleted. It also define indexes (keys), specify links between tables, and impose constraints between tables. The most important DDL statements in SQL are:
• 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

Basic SQL Queries:

//Creating a New Database

Create database mysampledb

Use mysampledb

//Creating New Table

A database most often contains one or more tables. Each table is identified by a name (e.g. "Customers" or "Orders"). Tables contain records (rows) with data.
Create table customers
(
C_Id int NOT NULL primary key,
LastName varchar(255) NOT NULL,
First Name varchar(255),
Address varchar(255),
City varchar(255)
)


//Insert Query

insert into customers values(1,'Aravind','kumer','Anna Nagar 12','Chennai')

insert into customers values(2,'Sundar','Rajan','Villivakkam 13','Chennai')

insert into customers values(3,'Hari','Ram','Perungudi 7','Chennai')

//select Query

select *from customers

select C_Id from customers

select LastName ,FirstName from customers

select Address from customers where C_Id=2

select *from customers where City='chennai'

//update query

update customers set City='chinnur' where C_Id=1


//Alter Column Name
alter table customers Address to Addr varchar(255)

sp_rename 'customers.Address' ,Addr

//Alter Table

//Rename table

sp_rename 'customers details' ,'customersdetails '

//Rename Column

sp_rename 'customers.Address' ,Addr

select *from customersdetails

//Add &drop Column

alter table customersdetails add dob datetime

alter table customersdetails drop column dob

//Distinct

select distinct City from customersdetails

//AND & OR Operators

select Addr from customersdetails where LastName='Hari' and FirstName='Ram'

select Addr ,City from customersdetails where C_Id=4 or LastName='Sundar'

//Order By

select *from customersdetails order by City