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Updating a cursor

The select for update forms puts on the row ensures o the row was not changed o the row will NOT be changed o the row is locked by you and you will be able to delete it. For Update and Group By cannot be used simultaneously. Tom, Just want to confirm the following : I have 4 identical (same code) processes running.

Actually, this update is somewhat flawed in concept, stk_flag sounds like it should be a derived column -- not a real column: create view v as select x.*, case when value = 75 then '*' end / the view is the right answer.

the update works but the data is immediately "questionable" since I could come along and upadte the value to 80 from 50 and the stk_flag isn't maintained the procedural code is just wrong in its approach.

Select for update is a programming tool -- use it when you need to. (not every transcation was using a for update nowait) April 09, 2003 - am UTC yes it is -- your application code is incorrect.

Tom, why does a SELECT FOR UPDATE statement still lock a row in the table, even though the select returned no rows? COLUMN Object_Name FORMAT A10 create table t1 ( a int , b int , c int ) / insert into t1 values (1,1,1); insert into t1 values (1,2,2); insert into t1 values (5,1,3); commit; update t1 set a = 3 where c = 2 / commit; SELECT do. One of the guys did it right -- they did a select for update, assuring them the row "is theirs".

Is there a way to give SELECT privilege with out FOR UPDATE capability?

March 03, 2004 - am UTC well, it is not "unknow" why it is holding the lock, they've ASKED for it.and t.rowid = :block.rowid FOR UPDATE NOWAIT; if that returns ORA-54 (resource busy), you are notified someone else has that row locked. Oracle_Username = 'SCOTT' / SELECT c FROM t1 WHERE a = 1 AND b = 2 AND c = 2 FOR UPDATE NOWAIT; SELECT do. The reason being use of function in the where predicate, since it will do the full scan and hence lock the whole table. Tom, The function in the query act upon 'bind variables', i am assuming this is also treated as a constant.if that returns 0 rows, you are told that the data has been modified -- you need to requery if that returns 1 row, you have the row locked and will be able to delete it and no one else can touch it. If you do not need to inspect the data BEFORE doing the delete, you do not need this logic in general. In your explanation you refered to variant(database column), what do u mean by variant? December 19, 2002 - am UTC meaning the value varies from row to row.It does this since you read the row out at time T1 and you delete it at time T2. There are no TX (transaction) locks -- hence no rows are locked in that table.It wants to make sure that in the time between T1 and T2 -- no one UPDATED that row. Dear Tom, Please consider this requirement: Field_Code Value Picked_up 10 10 No 20 15 No 10 20 No All the records with "Picked_up=No" are to be selected and populated into another table with "group by" on Field_Code, i.e.Do we care if someone tries to update them at the same time ?Also, if the result that was to be achieved with a combination of SELECT FOR UPDATE and DELETE CURRENT OF statement could be done in a single delete statement (with a sub-query) can it be error-prone in a multi-user env ?they have a bug in their code, they need to correct such a bug and understand when to actually use "for update". Tom, I issue a command : LOCK TABLE a IN ROW SHARE MODE NOWAIT; How do I unlock the table ? I searched for UNLOCK TABLE or RELEASE TABLE commands but to no avail.Thanks for your help March 24, 2004 - am UTC commit; rollback; thats the only way to release locks gained by SQL like that.If you need to inspect the data before the delete -- YOU NEED this logic (to ensure the data does not change under the covers). select * from t where column1 = column2; there -- column2 is "variable" when compared to column1.So, if you have coded: declare cursor c1 is select * from t where .... The value for column2 must be evaluated for each row.

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