Update table with constrained values from another table - sql-server

Question

I'm fairly new to SQL and tried solving this problem for about two days now, to no avail.
The question is, how can I update values in table Table_1 from values in Table_2, considering only specific subset of rows in Table_2, and without using cursors if possible.
More specifically, I have these two tables:
CREATE TABLE [dbo].[Table_1](
[ID] [int] NOT NULL,
[LastAmount] [int] NOT NULL,
[LastDate] [datetime] NOT NULL
) ON [PRIMARY];
CREATE TABLE [dbo].[Table_2](
[ID] [int] NOT NULL,
[Amount] [int] NOT NULL,
[Date_] [datetime] NOT NULL
) ON [PRIMARY];
In the tables there are following values:
INSERT INTO [dbo].[Table_1]
VALUES (1, 0, CONVERT(DATETIME, '19000101', 112)),
(2, 0, CONVERT(DATETIME, '19000101', 112));
INSERT INTO [dbo].[Table_2]
VALUES (1, 10, CONVERT(DATETIME, '19750101', 112)),
(1, 20, CONVERT(DATETIME, '19500101', 112)),
(1, 15, CONVERT(DATETIME, '20000101', 112)),
(2, 30, CONVERT(DATETIME, '20100101', 112));
The point is to update values in Table_1 where ID matches Table_2.
Table_1.LastAmount should get Table_2.Amount with the most recent Table_2.Date_. Similarly for Table_1.LastDate it should get Table_2.Date_ where the date is the most recent for that specific ID.
So, Table_1 before update:
ID |LastAmount |LastDate
----|-----------|--------
1 |0 |1900-01-01 00:00:00.0000
2 |0 |1900-01-01 00:00:00.0000
Table_2:
ID |Amount |Date
----|-----------|--------
1 |10 |1975-01-01 00:00:00.0000
1 |20 |1950-01-01 00:00:00.0000
1 |15 |2000-01-01 00:00:00.0000
2 |30 |2010-01-01 00:00:00.0000
Table_1 after update:
ID |LastAmount |LastDate
----|-----------|--------
1 |15 |2000-01-01 00:00:00.0000
2 |30 |2010-01-01 00:00:00.0000
I tried all kinds of UPDATE with INNER JOIN, or using an inline SELECT when assigning the value, but none of them worked. Many thanks in advance.

Answer 1

An update from is useful in this situation. row_number() is used here with the source table to determine the most recent entry in Table_2.
update
Table_1
set
LastAmount = T2.Amount
,LastDate = T2.Date_
from
(
select
ID
,Amount
,Date_
,row_number() over (partition by ID order by Date_ desc) as RowNumber
from
Table_2
) T2
where
Table_1.ID = T2.ID
and T2.RowNumber = 1

Answer 2

Do like this:
Update Table_1
Set LastAmount = Table_2.Amount,
LastDate = Table_2.[Date_]
from (SELECT ID, MAX([Date_]) as MaxDate FROM TABLE_2 GROUP BY ID) AS Max_Table2
inner join Table_2 on Max_Table2.MaxDate = Table_2.[Date_] and Max_Table2.id = Table_2.id
inner join table_1 on table_1.id = Table_2.id
Basically you have filter the table2 to get the max date and join everything up to find the lastdate and amount.

Answer 3

It's a simple use of ROW_NUMBER() and a CTE to do this:
;With Ordered as (
select ID,Amount,Date_,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Date_ DESC) rn
from Table_2
)
update t1
set LastAmount = o.Amount,
LastDate = o.Date_
from
Table_1 t1
inner join
Ordered o
on
t1.ID = o.ID and
o.rn = 1
(You could write it as a subquery rather than a CTE, but I picked a CTE in this example)