SQL Query

I was wondering if someone can tell me what I’m doing wrong here.

insert into Table1
(Column1)
select N.Column2
from Table2 N
, Table1 A
where N.Column3 = A.Column3

This statement is meant to insert the value in Column2 into another table with column name being Column1 when both Column3 numbers are equal in both tables.

When I run the script it says 727 rows affected, but when I run a select statement to see the results, it all looks exactly the same. What is it updating? And why isn’t inserting the data into column1?