Is it possible to use MAX in update statement usin

问题:

i am trying to use the MAX function in sql statement. Here is what i am trying to do: something like this:

UPDATE MainTable
        SET [Date] = GETDATE()

        where [ID] = Max

I know this is wrong specially where i put the where condition but cannot figure out how to use max and update in the same statement. thanks

回答1:

UPDATE MainTable
   SET [Date] = GETDATE()
 where [ID] = (SELECT MAX([ID]) FROM MainTable)

回答2:

One way

DECLARE @MaxID INT = (select MAX(id) FROM MainTable)

UPDATE MainTable
        SET [Date] = GETDATE()
        where [ID] = @MaxID

That is SQL 2008 syntax, in 2005 you need to do the declaraion and assignment of the variable in two steps

You could also use a common table expression

;WITH cte
AS (
SELECT TOP 1 * FROM MainTable
ORDER BY ID DESC

)

UPDATE cte SET [Date] = GETDATE()

Example you can run

CREATE TABLE testNow(id int)
INSERT testNow VALUES(1)
INSERT testNow VALUES(2)

;WITH cte
AS (
SELECT TOP 1 * FROM testNow
ORDER BY ID DESC

)

-- id with 2 will become 5
UPDATE cte SET ID = 5

SELECT * FROM testNow

Output

1
5

回答3:

UPDATE MainTable
SET [Date] = GETDATE()
WHERE [ID] = (SELECT MAX(your column) FROM yourtable)