Hello All, I am using oracle 11gr2 on windows server 2008. This is a test system.Stats are current and archivelog is turned off temporarily. I am trying to update a table that has over 1.1 million rows. I have a simple update statement that does the following. (basically updates mycolumn when it is null, to somevalue) update mytable a set a.mycolumn = (select b.mycolumn from mytable b where a.joincolumn = b.joincolumn and b.anothercol='someval') where a.mycolumn is null; The number of rows where mycolumn is null is around 1/5th of the total. (225000 rows) The above update statement seems to be running forever.On checking the explain plan this is what i see. --------------------------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | --------------------------------------------------------------------------------------------------------- | 0 | UPDATE STATEMENT | | 224K| 2630K| 6454M (1)|127:19:43 | | 1 | UPDATE | mytable | | | | | |* 2 | TABLE ACCESS FULL |mytable | 224K| 2630K| 6644 (1)| 00:00:01 | |* 3 | TABLE ACCESS BY INDEX ROWID| mytable | 1 | 21 | 28752 (1)| 00:00:03 | |* 4 | INDEX RANGE SCAN | mytable_someval_INDEX | 874K| | 3318 (1)| 00:00:01 | --------------------------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 2 - filter("a"."mycolumn" IS NULL) 3 - filter("b"."joincolumn"=:B1) 4 - access("b"."anothercol"='somecol') I know i can use CTAS to achieve my task.However i am not sure why updating a .225 million rows would take hours. Can my update statement be written more efficiently? (perhaps using merge update?) Maybe there is some other bottleneck that I need to look? Any thoughts would be very well appreciated. Thanks!!! -- *Thousands of candles can be lighted from a single candle, and the life of the single candle will not be shortened. Happiness never decreases by being shared.*