Updating oracle table from a join rosie odonnells ex is dating who
The Oracle UPDATE statement is used to update existing records in a table in an Oracle database.There are 2 syntaxes for an update query in Oracle depending on whether you are performing a traditional update or updating one table with data from another table.You can trace these spills (in SQL Server 2008) using the Profiler events Hash Warnings and Sort Warnings.The estimate for the hash table's build input is very good: The estimate for the sort input is less accurate: You would have to use Profiler to check, but I suspect the sort will spill to in this case.update tab a set col1 = -1 from tab b where a.col2 = b.col2 and a.col3 = b.col3 and a.col3 = b.col4 Can anyone throw some light on this? I looks like it should be something like this: update a set col1 = -1 from tab a, tab b where a.col2 = b.col2 and a.col3 = b.col3 and a.col4 = b.col4 HTH, Ananthram" id="ctl00_m_m_i_ctl00_gr_ctl01_bestanswerbody" class="textarea-bestanswerhidden" name="bestanswerbody" answerbody Id="5190317" / update tab a set col1 = -1 where exists (select 1 from tab b where a.col2 = b.col2 and a.col3 = b.col3 and a.col3 = b.col4 ) Method 2: update tab a set (col1,col7,col8) = (select -1, col7,col8 from tab b where a.col2 = b.col2 and a.col3 = b.col3 and a.col3 = b.col4 ) where exists (select 1 from tab b where a.col2 = b.col2 and a.col3 = b.col3 and a.col3 = b.col4 ) Note: In Method 2 the sub-query must return only 1 row.
The hash join is a less obvious choice, because it's inputs are similar sizes (to a first approximation, anyway).
Well I can't see the full script, but it seems like you're adding a column with a value (identity) to an existing table, so the existing rows will have to grow.
If there isn't space on the page, it will split, and you will end up with a very fragmented table (clustered index).
It is also possible that the hash table spills too, but that is less clear-cut.
Note that the memory reserved for this query is split between the hash table and sort, because they run concurrently.
The big drawback with the nested loops plan is that it runs on a single thread.