--- CODE-1 ---
Select E.Name as Employee, isnull(M.Name, 'No Manager')as Manager
from Manager E
left join Manager M
on e.ManagerID =m.EmployeeId

--- CODE-2 ---
Select E.Name as Employee,
case
When M.Name is null Then 'No Manager' Else M.Name
End
as Manager
From Manager E
left join Manager M
on e.ManagerID =m.EmployeeId

--- CODE-3 ---
Select E.Name as Employee,coalesce(m.Name, 'No Manager') as Manager
From Manager E
left join Manager M
on e.ManagerID =m.EmployeeId

#NULL qiymatni yozuvga almashtirish **Faqat ekranga chiqarishda almashadi

#Coalesce — Jadvaldagi null qiymatni o'rniga o'ng tomondagi birinchi null bo'lmagan qiymatni tortadi

#Union ikkalasida takrorlanadiganidan faqat bttasini oladi Union all takrorlanishlarni ham oladi

create table india (
id int identity (1,1) primary key,
[Name] nvarchar(123) not null,
Email nvarchar(123) not null,
)
insert into india([Name],Email)
values ('Raj','r@r.com'),('Sam','s@s.com')

create table uk (
id int identity (1,1) primary key,
[Name] nvarchar(123) not null,
Email nvarchar(123) not null,
)
insert into uk([Name],Email)
values ('Ben','b@b.com'),('Sam','s@s.com')

select * from uk

select * from india

Select * from india
union
select * from uk


Select * from india
union all
select * from uk

#union va union all farqi

#Except — A jadvaldan B jadvalda ham bor bo'lgan qiymatni olib tashlash uchun ishlatiladi

#Except 2

#Except 3

Google Lens orqali tarjima qilindi. Sinab ko‘ring!
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SQL HAVING Tutorial | LearnSQL.com
https://learnsql.com/blog/sql-having-clause-tutorial/

#Coalesce create table AAAA(
id int identity(1,1) primary key,
fn nvarchar (123),
mn nvarchar (123),
ln nvarchar (123)
)
insert into AAAA
values ('sam',null,null),(null,'Tod','Tarzan'),(null,null,'Sara')
,('Ben','parkovka',null),('Jamshid','fensi','Ferferro')
select * from AAAA

select id, coalesce(fn,mn,'Fakaferro')
from AAAA