update each row without where clause

I have a table... 12,098 records.. first column is PK

there is a temp table that has 9876 rows (one column only - unique values)

for testing purpose i have to update only the PK in main table for the first 9876 rows with the values from the temp table..

how could you do that in one query in T-SQL?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

So you want the PK of the first row in your table to be changed to be the value of the first row in your temp table? And then the PK of the second row in your table to be changed to be the value of the second row from your temp table? And so on, until the temp table is exhausted?

Patrick TallaricoDecision Support and Systems AnalystCommented:
I have to assume that there is no way to link the tables through a join using existing data, therefore, can you order the Main table in such a way that all the values in that table will correctly correspond with the values to be replaced from the temp table?  If you can't order the main table properly, then you might have to create an extra column to help signify the top 9876 that you actually wish to edit. The lack of relational data makes this tricky.

if so, you could try something like the following.  Word of caution, try this on copies of the tables first so as to protect the original data.  

Update maintable
set column1 = t.column1
from (select rownumber() as 'rn',* from maintable order by column1 ) as m
         inner join
         (select rownumber() as 'rn',column1 from temptable ) as t
     on m.rn = t.rn

This query should assign a row number to the main table properly ordered to match the temp table.  You should be able to add the Order By into the select statement for the temp table too if you need.  Also you can adjust the order by in the select statement for the main table to order it by any column you wish.

Another less friendly approach would be to use a cursor to move through the records of the main table one by one, but again, this would require that both tables be ordered properly to ensure the proper replacement values.
25112Author Commented:
Tom, that is the idea..
Acronis True Image 2019 just released!

Create a reliable backup. Make sure you always have dependable copies of your data so you can restore your entire system or individual files.

25112Author Commented:
stpmt11, i am trying with your idea.. i will let you know
25112Author Commented:
stpmt11, i am getting
Violation of PRIMARY KEY constraint ... Cannot insert duplicate key in object . The duplicate key value is (474157).

how to avoid it?

Update maintable
set column1 = t.tempcolumn
(select row_number() OVER (order by column1) as 'rn',* from maintable) as m
   inner join
(select row_number() OVER (order by tempcolumn) as rn , tempcolumn from temptable ) as t

on m.rn = t.rn where m.column1 <>  t.tempcolumn
Patrick TallaricoDecision Support and Systems AnalystCommented:
it sounds like there are values in the temp table that match values that would remain in the table after the update.  Perhaps you should compare the temp table to the main table to see how many matching values the tables contain.  You could replace the main table's key values with the rownumber values first, then try the update.  This is assuming that the only matching keys appear in the first 9876 rows.
25112Author Commented:
isn't the condition where m.column1 <>  t.tempcolumn enough to disqualify where there is a match?
Patrick TallaricoDecision Support and Systems AnalystCommented:
Because you are matching the row number columns, the query doesn't compare the two table's key values, with the exception of if they have the same column number.  

If we take the first list as the temp table, and the second as the main, we can expect the where clause to catch the second row, since both the rows match, but it would still error out from the duplicate column value in row 4 of the main table matching the row 1 value of the temp table.
I suggest running a query on the two tables to first compare the keys of both tables and see what matches come up.
awking00Information Technology SpecialistCommented:
As has been explained, there is likely a value in a row of the temp table that matches a value for the primary key in the main table that is in a higher row, causing a primary key violation. You might try altering the table to remove the primary key constraint, do the update, then re-create the primary constraint.
Patrick TallaricoDecision Support and Systems AnalystCommented:
@awking has a good idea, just a caution, however, you may end up with duplicate values in the key column that you would then have to resolve before you could add the primary key back.
It might be best to create a JOIN of the two tables by row number and INSERT the result into a new temp table. Then clear the original table and rebuild it from the new temp table.

It simply might not be possible to eliminate duplicates any other way. Further, examination of the new temp table would show where all cleanup might be needed.


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
25112Author Commented:
implemented your suggestion.. many thanks
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Microsoft SQL Server 2008

From novice to tech pro — start learning today.