SQL Server 2022

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CREATE TABLE Table1(id int, name varchar(5))
CREATE TABLE Table2(id int, name varchar(5))
INSERT INTO Table1 VALUES (1,'abc'), (2,'xxx'), (3, 'mm')
3 rows affected

INSERT INTO Table2 VALUES (1,'abcd'), (3, 'nnnn')
2 rows affected

select Table1.Id, 
case WHEN Table2.Name IS NULL
     then Table1.Name
    else Table2.Name 
end as Name
from Table1
left join Table2 on Table2.Id = Table1.Id


Id
Name


1
abcd

2
xxx

3
nnnn