Question

I need to take data from one table and import it into another table. In pseudocode, something like this:

For Each row in table1
If row.personid is in table2 then
   update table2.row
Else
   insert row into table2
End If
Next

What is the best way to do this in T-SQL? As I understand it T-SQL doesn’t support For Each..Next, so what alternatives do I have?

Answer 1

All things being equal, set based operations are better.

update t1
set t1.x = t2.x
.
.
.
from table1 t1
inner join table2 t2 on t1.id = t2.t1id

then

insert into table1
select * from table2 t2 where t2.t1id not in (select table1.id from table1 )