SQL Server 2019

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select @@version;

(No column name)
Microsoft SQL Server 2019 (RTM-CU3) (KB4538853) - 15.0.4023.6 (X64) Mar 4 2020 00:59:26 Copyright (C) 2019 Microsoft Corporation Express Edition (64-bit) on Windows Server 2019 Standard 10.0 <X64> (Build 17763: ) (Hypervisor)

create table tableA(number int, [Status] varchar(10))

insert into tableA select 1111, 'C'

insert into tableA select 2222, 'O'

insert into tableA select 3333, 'O'

insert into tableA select 4444, 'C'

create table tableB(number int, [Status] varchar(10))

insert into tableB select 1111, 'c'

insert into tableB select 2222, 'O'

insert into tableB select 5555, 'C'

insert into tableB select 6666, 'O'

create table tableC(number int, [Status] varchar(10))

Insert into TableC (number,[Status])

Select a.number,a.Status from TableA a

left join TableB b ON b.number = a.number

where B.number is Null

select * from tableC

number	Status
3333	O
4444	C