How does this UPDATE update multiple rows?

Question

For the UPDATE in the following script, what values are selected to update Table2? For example, for a row in Table2 (ie. 'NY') there are several rows in Table1 that can be used for the update.
Thanks.
create table Table1
Col1 varchar(10),
Col2 varchar(10),
Col3 varchar(10)
Insert into Table1
select 'FL', 2, 2
union
select 'FL', 2, 2
union
select 'FL', 2, 5
union
select 'FL', 2, 3
union
select 'NY', 2, 2
union
select 'NY', 1, 3
union
select 'NY', 2, 2
union
select 'NY', 2, 3
union
select 'CA', 3, 2
union
select 'CA', 5, 1
union
select 'CA', 4, 2
union
select 'CA', 2, 3
create table Table2
Col1 varchar(10),
Col2 varchar(10),
Col3 varchar(10),
Ignore varchar(10)
Insert into Table2 (Col1, Ignore)
select 'FL', 1
union
select 'FL', 2
union
select 'FL', 3
union
select 'FL', 4
union
select 'NY', 5
union
select 'NY', 6
union
select 'NY', 7
union
select 'NY', 8
union
select 'CA', 9
union
select 'CA', 10
union
select 'CA', 11
union
select 'CA', 12
update T2
set Col2 = T1.Col2,
Col3 = T1.Col3
from Table1 T1 inner join Table2 T2
on T1.Col1 = T2.Col1
select col1, col2, col3 from Table1
select col1, col2, col3 from table2
VM

Answer 1

When you use Merge syntax, it will not run. You can check the error message:
create table Table1
Col1 varchar(10),
Col2 varchar(10),
Col3 varchar(10)
Insert into Table1
select 'FL', 2, 2
union
select 'FL', 2, 2
union
select 'FL', 2, 5
union
select 'FL', 2, 3
union
select 'NY', 2, 2
union
select 'NY', 1, 3
union
select 'NY', 2, 2
union
select 'NY', 2, 3
union
select 'CA', 3, 2
union
select 'CA', 5, 1
union
select 'CA', 4, 2
union
select 'CA', 2, 3
create table Table2
Col1 varchar(10),
Col2 varchar(10),
Col3 varchar(10),
Ignore varchar(10)
Insert into Table2 (Col1, Ignore)
select 'FL', 1
union
select 'FL', 2
union
select 'FL', 3
union
select 'FL', 4
union
select 'NY', 5
union
select 'NY', 6
union
select 'NY', 7
union
select 'NY', 8
union
select 'CA', 9
union
select 'CA', 10
union
select 'CA', 11
union
select 'CA', 12
Merge Table2 T2
Using Table1 T1
on T1.Col1 = T2.Col1
When Matched Then
UPDATE
set Col2 = T1.Col2,
Col3 = T1.Col3;
Msg 8672, Level 16, State 1, Line 64
The MERGE statement attempted to UPDATE or DELETE the same row more than once. This happens when a target row
matches more than one source row. A MERGE statement cannot UPDATE/DELETE the same row of the target
table multiple times. Refine the ON clause to ensure a target row matches at most
one source row, or use the GROUP BY clause to group the source rows.
--select col1, col2, col3 from Table1
--select col1, col2, col3 from table2
--drop table table1
--drop table table2