Question : Simple MySQL query to update a table with different values from same table

Hello,

I have a table (simplified) with the following rows

Code   Value    Year
1         NULL      2009
1         123         NULL
2         NULL      2009
2         234        NULL
3         NULL      2009
3         345         NULL

I want to update all the 2009 records for each code, with the equivalent value where year=NULL. There will never be more than one 2009 and one NULL record for each code, but there may not always be both for each code.

I think this ought to be a very simple query, but not quite sure how to figure it out. I am hoping someone can give me a failsafe solution- I have large tables and am on a shared host and don't want to run a query that gets stuck and affects the performance of other sites on the host.  

Thanks very much!

Answer : Simple MySQL query to update a table with different values from same table

do you mean this? :

UPDATE table1 t1 JOIN table1 t2 ON t1.code= t2.code
SET t1.Value=t2.value
where t1.year=2009 and t2.year is null