SQL update table by targeting unique row one int less - sql

Question

What I have is a table with the following columns
All columns are nvarchar expect for the Date columns which are datetime
CreateDateA InvIDA StorageIDA CreateDateB InvIDB StorageIDB UniID
What I want to do is move the values on each row (based on UniID) into the represenative B columns where UniID is 1 less, so the 'A' columns where UniID = 2 should go to the B Columns where the UniID = 1.
This is the query i'm using but it's not updating any columns.
update InvSubmission
set CreateDateB = CreateDateA,
InvIDB = InvIDA ,
StorageIDB = StorageIDA
where StorageIDB = StorageIDA and UniID = (select UniID-1 from InvSubmission)
There is multiple storageid's in this table, however, each record has a match to at least one other row.

Answer 1

#PinnyM's answer is close, but in SQL Server, you have to name the updated table in the from clause also:
update toUpdate
set CreateDateB = sourceTable.CreateDateA,
InvIDB = sourceTable.InvIDA
FROM
InvSubmission toUpdate
inner Join
InvSubmission sourceTable
ON sourceTable.UniID = toUpdate.UniID + 1
AND sourceTable.StorageIDA = toUpdate.StorageIDB
Otherwise, this note becomes relevant:
If the object being updated is the same as the object in the FROM clause and there is only one reference to the object in the FROM clause, an object alias may or may not be specified
And then you're suffering the same problem that #Yuck pointed out - you're trying to compare the UniID value within a single row to a value one less than itself.

Answer 2

UniID = (select UniID-1 from InvSubmission) is equivalent to UniID = UniID - 1. So, for example, you're basically saying:
WHERE 2 = (2 - 1)
And that's never going to be true, which is why the query isn't modifying anything.
If both the A and B columns are in the same row you don't even need to qualify by using the ID clause. Otherwise you need to self-join like this:
update InvSubmission
set CreateDateB = B.CreateDateA,
InvIDB = B.InvIDA ,
StorageIDB = B.StorageIDA
from InvSubmission A INNER JOIN
InvSubmission B ON A.UniID = B.UniId - 1
where A.StorageIDB = A.StorageIDA;
As I mentioned it's a little confusing because your example makes it look like the columns are all contained in the same row...

Answer 3

It may actually depend on which RDBMS you are using (some are finicky on how aliases can be used), but you can try:
update InvSubmission
set CreateDateB = sourceTable.CreateDateA,
InvIDB = sourceTable.InvIDA ,
StorageIDB = sourceTable.StorageIDA
FROM InvSubmission sourceTable
WHERE sourceTable.UniID = InvSubmission.UniID + 1