SQL Tutorial 7: Cross Join, Self Join and Coalesce

Learn SQL, Introduction to DML: How to create a cross join, self Join. Need of coalesce, nvl, isnull, and ifnull function. #sql, #rdbms, #table, #amitchandakda #interviewquestions #interview

Definition Source: Google Search, Wikipedia, IBM, W3School

00:00 Introduction
03:00 SQL Cross Join
08:30 SQL Self Join

SQL Tutorial 6, Select with Group By and Having plus Where: https://youtu.be/gTrOz7Sj-QE

-- SQL

select s.qty , i.name
from sales s
inner join item i
on i.item_id = s.Item_ID;


select s.qty , i.name
from sales s
, item i
;

select s.qty , i.name
from sales s cross join item i
;

select distinct Brand, Category
from item

--Create table brand as
select distinct Brand
into Brand
from item;

--Create table Category as
select distinct Category
into Category
from item;

select * from Brand;

select * from Category;

select *
from Brand cross join Category

select b.Brand as Brand , c.Category as cat
from Brand b cross join Category c


-- Create table brand_cat as
select b.Brand as Brand , c.Category as cat
into brand_cat
from Brand b cross join Category c

select * from brand_cat


-- Self Join
Create table emp
(emp_id int ,
mrg_id int ,
name varchar(50)
);

insert into emp
values(1,null, 'Amit')
, (2,1, 'Sumit')
, (3,1, 'Anil')
, (4,2, 'Ajay')
, (5,2, 'Vijay');

select * from emp;



select e.name, m.name as mrg_name
from emp e
inner join emp as m
on e.mrg_id = m.emp_id;


select e.name, coalesce(m.name,e.name) as mrg_name
from emp e
left join emp as m
on e.mrg_id = m.emp_id

-~-~~-~~~-~~-~-
Please watch: "Microsoft Power BI Tutorial For Beginners✨ | Power BI Full Course 2023 | Learn Power BI"
https://www.youtube.com/watch?v=cN8AO3_vmlY
-~-~~-~~~-~~-~-