Update query using Subquery in Sql Server

Solution 1:

you can join both tables even on UPDATE statements,

UPDATE  a
SET     a.marks = b.marks
FROM    tempDataView a
        INNER JOIN tempData b
            ON a.Name = b.Name

• SQLFiddle Demo

for faster performance, define an INDEX on column marks on both tables.

using SUBQUERY

UPDATE  tempDataView 
SET     marks = 
        (
          SELECT marks 
          FROM tempData b 
          WHERE tempDataView.Name = b.Name
        )

• SQLFiddle Demo

Solution 2:

because you are just learning I suggest you practice converting a SELECT joins to UPDATE or DELETE joins. First I suggest you generate a SELECT statement joining these two tables:

SELECT *
FROM    tempDataView a
        INNER JOIN tempData b
            ON a.Name = b.Name

Then note that we have two table aliases a and b. Using these aliases you can easily generate UPDATE statement to update either table a or b. For table a you have an answer provided by JW. If you want to update b, the statement will be:

UPDATE  b
SET     b.marks = a.marks
FROM    tempDataView a
        INNER JOIN tempData b
            ON a.Name = b.Name

Now, to convert the statement to a DELETE statement use the same approach. The statement below will delete from a only (leaving b intact) for those records that match by name:

DELETE a
FROM    tempDataView a
        INNER JOIN tempData b
            ON a.Name = b.Name

You can use the SQL Fiddle created by JW as a playground

Solution 3:

Here in my sample I find out the solution of this, because I had the same problem with updates and subquerys:

UPDATE
    A
SET
    A.ValueToChange = B.NewValue
FROM
    (
        Select * From C
    ) B
Where 
    A.Id = B.Id