the multi part identifier could not be bound in an update query - sql

Question

First of all I've looked at similar questions but failed to find one for my case.
The access code i am turning into sql is as follows (I didn't write it)
UPDATE QUpdateTrialstepApproved1
INNER JOIN TrialStepApproved ON
QUpdateTrialstepApproved1.cid_req = TrialStepApproved.cID
SET TrialStepApproved.wm21 = [wm2_req],
TrialStepApproved.sw = [startweek_req],
TrialStepApproved.PlannedTotalm2 = [m2_req],
TrialStepApproved.ew = [endweek_req],
TrialStepApproved.ActualNrofDiffEntries = [entries_req],
TrialStepApproved.entryfactorTrial1 = [eFtrial_req],
TrialStepApproved.fixeddeliveryweek = [fixedEndweek_req],
TrialStepApproved.culturename = [culturename_req]
WHERE (((QUpdateTrialstepApproved1.approveRequestChange)="v")
AND ((TrialStepApproved.Location) Is Not Null));
I've turned it into the following but I get the error in the title:
UPDATE A
SET B.wm21 = [wm2_req],
B.sw = [startweek_req],
B.PlannedTotalm2 = [m2_req],
B.ew = [endweek_req],
B.ActualNrofDiffEntries = [entries_req],
B.entryfactorTrial1 = [eFtrial_req],
B.fixeddeliveryweek = [fixedEndweek_req],
B.culturename = [culturename_req]
from QUpdateTrialstepApproved1 as A
INNER JOIN TrialStepApproved as B ON A.cid_req = B.cID
WHERE A.approveRequestChange='v' AND B.Location Is Not Null

Answer 1

You're updating B, not A. Change the first line to
UPDATE B
...and thing will work fine.
An SQLfiddle.