How do i join on null in two table in sql? inner join, left,right,full n cross join -- Interview Question Tech Mahindra

Question

Create table TechM ( id int ) ;

select * from TechM insert into TechM values (1), (1), (1),
(2), (3), (null) ;

Create table TechN ( id int ) ;

select * from TechN insert into TechN values (1), (1), (2),
(2), (2), (2), (null), (4), (5), (null) ;

Answer 1

Each NULL is considered to be a different value, So In this case count will be as below

Left join -- 12
Right join -- 14
Full join --16
Cross join -- t1*t2 = 6*10 = 60 

you can see the count/query on below link in detail : check here

These type of question is commonly asked in interview.