Link to home
Start Free TrialLog in
Avatar of enrique_aeo
enrique_aeo

asked on

rowid

please, can you explain it means rowid

SOLUTION
Avatar of Sean Stuber
Sean Stuber

Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
Avatar of enrique_aeo
enrique_aeo

ASKER

select   ...
from tmp_Solicitud ts
where (ts.CodUnico, ts.rowid) in
      (
      select t.CodUnico, min(t.rowid)
      from tmp_Solicitud t
      group by t.CodUnico
      );

and used in the where?
SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
ASKER CERTIFIED SOLUTION
Link to home
membership
This solution is only available to members.
To access this solution, you must be a member of Experts Exchange.
Start Free Trial
note that you should never "remember" a rowid for later use... between the time you fetched it and want to use it again, the row might have been moved, and hence changed it's row id.
this is occuring when rows are updated, deleted and inserted into the table (it might be because of other rows modified that "your" row gets a new rowid, hence !
The ROWID is an encoded address to where a row physically resides, namely to the Oracle datafile number, block number within the datafile and row number within the block.

Your select is just trying to get only one row for each t.CodUnico. If you don't really use the rowid, it would give the same results if you use MAX(t.rowid). It's just a way to choose one row among many "similar" ones. You can just as well replace it in the inner subquery with (select DISTINCT CodUnico from tmp_Solicitud).

Now, if below that select it does something with the fetched rowid, don't mess with the code too much before contacting the original coder.
Others have explained already what "rowid" is in Oracle.  You had asked for a way to get just the unique (or "distinct") CodUnico values from a table, so the query I gave you did that by using "group by CodUnico" along with a group operator (min) on another column.  Since "rowid" is a logical address for a single record in Oracle, I used "min(rowid)" in that query to just find the "first" row that matched the CodUnico value.  But, as stsuber indicated, this does not guarantee that the other columns of this row have the values you want.