UPDATE UPI_ATTRIBUTE SET SITE_INC ='0'
WHERE USER_PROFILING_NAME IN ('CAR_IMPLICIT','CAR_EXPLICIT')
Above is my query that I am using to update the columns in UPI_ATTRIBUTE table. And suppose if I need to rollback the above changes that I am doing with update query, then how can I use the delete query in the above case? Currently SITE_INC is empty. So after updating the table it will have 0 in that. And If I need to rollback the changes then I need to make it empty again.
How can I delete the value 0 from above column after updating.
You cannot "delete" data to rollback an update.
Even if the only change that you'll do is set a flag from "NULL" to "Y" and vice versa, you can't really determine which value to update when you do multiple updates.
update 1 : set from "NULL" to "0"
update 2 : set from "0" to "something else"
update 3 : Rollback changes (rollback to which state)?
If you want to really rollback changes to specific rows (instead of the complete table, which can be done using Flashback), you can audit the changes to "remember" the values and then revert back to them.
Even then, you should consider which point to revert to, when you have multiple updates.
Not sure Oracle have final table/old table function for select/update.
For DB2 for z/OS, it have such function:
SELECT LASTNAME, BONUS FROM FINAL TABLE
(UPDATE EMP SET BONUS = BONUS * 1.3
WHERE JOB = 'CLERK');
Then, the result set of the select include all the updated rows. you can use rownum or other unique value, then you can update it back to any value as you want.
Related
I have this table:
When I make a delete of a box in this table, I need to make an increment of all the following rows.
For example: if I delete BoxNo '4' then the rows which are after the last row of BoxNo '4' (5,6,7,..etc) have to make an increment by 1 and be like (4,5,6,...etc.). I hope I succeed in explaining the problem.
Could you please kindly help me to perform this with an SQL Server query?
Thanks in advance.
Executing actions automatically after rows are deleted is what TRIGGERS are for.
In your case, it looks something like:
CREATE TRIGGER MyTable_AfterDelete
ON MyTable
FOR DELETE
AS
update MyTable set RowCounter = RowCounter + 1
from deleted
inner join MyTable on MyTable.BoxNo > deleted.BoxNo
GO
As you can see SQL Server doesn't raise a trigger after each row deleted but after each DELETE statement execution, which can involve several rows deleted, so we need to use the "deleted" pseudo-table to apply our action on every one of those rows deleted.
PS: This is how what you asked can be done, although I agree with the comments that say that you could structure better this problem instead of needing to update so many rows after every delete.
UPDATE
If you want to execute it manually on every delete instruction, instead of automatically on a trigger, you can pass a parameter to your DELETE statement on C# in order to update the posterior RowCounters. Something like:
delete from MyTable where BoxNo = #BoxNo
update MyTable set RowCounter = RowCounter + 1 where BoxNo > #BoxNo
Suppose we have table A with fields time: date, status: int, playerId: int, serverid: int
We added constraint on time, playerid and serverid (UNQ_TIME_PLAYERID_SERVERID)
At some time we try to update all rows in table A with new status and date:
update status = 1, time = sysdate where serverid=XXX and status != 1 and time > sysdate
Problem that there are two separated processes on separate machines that can execute same update at same sysdate.
And UNQ_TIME_PLAYERID_SERVERID violation occurs!
Is there any possibility to force Oracle check where cause before concrete update (when lock on row acquired)?
I do not want to use any 'select for update' things
If it's really the same update 100% of the time, then just catch the exception and ignore it.
In case you want to prevent an error occuring in the first place, you need to implement some logic to prevent the second update statement from ever executing.
I could think of a "lock table" just for this purpose. Create a table TABLE_A_LOCK_TB (add columns based on what information you want to have stored there for administrative reasons, e.g. user who set the lock or a timestamp, ...).
Before you execute an update statement on table A, just insert a row to TABLE_A_LOCK_TB. Once an update was successful, delete said row.
Before executing any update statement on table A just check whether the TABLE_A_LOCK_TB has a dataset. If it doesn't your update is good to go, if it does you don't execute the update.
To make this process easier you could just write a package for "locking" and "unlocking" table A by inserting / deleting a row from the TABLE_A_LOCK_TB. Also implement a function to check the "lock status".
If you need this logic for several tables you can also make it dynamic by just having a column holding the table name in TABLE_A_LOCK_TB and checking against that.
In your application logic you can handle every update like this then (pseudocode):
IF your_lock_package.lock_status(table_name) = false THEN
your_lock_package.set_lock(table_name);
-- update statement(s)
your_lock_package.release_lock(table_name);
ELSE
-- "error" handling / information to user + exit
How can I delete the value of a field from a database, using query code? I only know where the field is located in the database. (ex: column['phone number']row[3])
It should be something like this "DELETE FROM ... WHERE ..."
There is nothing like delete the field in database i.e. if you want to remove the complete row then you can do that easily like this
DELETE FROM TABLE WHERE COLUMN1=#myValue
But if you wanted to remove one value of the row in that case you should update that value as NULL
UPDATE TABLE SET COLUMN1=NULL WHERE COLUMN1=#myValue
I have used where clause from my imagination. you can always use whatever you want.
The DELETE statement allows you to delete RECORDS.
When you want to set a field to an empty value, use the UPDATE statement.
See this for more info.
UPDATE [YOUR_TABLE] SET [YOUR_FIELD] = NULL WHERE [YOUR_PRIMARY_KEY] = VALUE
Yes first you need to use delete command. Then after this insert update command then only the records will be deleted from the database. I agree that you have deleted records but its not showing because you haven't updated it.
I am making some tweaks to a legacy application built on SQL Server 2000, needless to say I only want to do the absolute minimum in the fear that it may just all fall apart.
I have a large table of users, tbUsers, with a BIT flag for IsDeleted. I want to archive off all current and future IsDeleted = 1 user records into my archive table tbDeletedUsers.
Moving the currently deleted users is straight forward, however I want a way to move any future users where the IsDeleted flag is set. I could use a standard AFTER trigger on the column however I plan to add some constraints to the tbUser table that would violate this, what I'd like is for my INSTEAD OF UPDATE trigger to fire and move the record to archive table instead?
I guess my question is... is it possible to trigger an INSTEAD OF UPDATE trigger on the update of an individual column? This is what I have so far:
CREATE TRIGGER trg_ArchiveUsers
INSTEAD OF UPDATE ON tbUsers
AS
BEGIN
...
END
GO
If so an example (SQL 2000 compatible) would be much appreciated!
Using the UPDATE(columnname) test, you can check in a trigger whether a specific column was updated (and then take specific actions), but you can't have a trigger fire only on the update of a specific column. It will fire as soon as the update is performed, regardless of the fact which column was the target of the update.
So, if you think you have to use an INSTEAD OF UPDATE trigger, you'll need to implement two kinds of actions in it:
1) insert into tbDeletedUsers + delete from tbUsers – when IsDeleted is updated (or, more exactly, updated and set to 1);
2) update tbUsers normally – when IsDeleted is not updated (or updated but not set to 1).
Because more than one row can be updated with a single UPDATE instruction, you might also need to take into account that some rows might have IsDeleted set to 1 and others not.
I'm not a big fan of INSTEAD OF triggers, but if I really had to use one for a task like yours, I might omit the UPDATE() test and implement the trigger like this:
CREATE TRIGGER trg_ArchiveUsers
ON tbUsers
INSTEAD OF UPDATE
AS
BEGIN
UPDATE tbUsers
SET
column = INSERTED.column,
…
FROM INSERTED
WHERE INSERTED.key = tbUsers.key
AND INSERTED.IsDeleted = 0
;
DELETE FROM tbUsers
FROM INSERTED
WHERE INSERTED.key = tbUsers.key
AND INSERTED.IsDeleted = 1
;
INSERT INTO tbDeletedUsers (columns)
SELECT columns
FROM INSERTED
WHERE IsDeleted = 1
;
END
I want to perform a update then select the result. I don't want anything to be able to update the row I am updating until after the select has occurred. How would I do this?
My goal is to increment a value of a row and return that incremented value. I have thus far found that I end up with an issue where update (to increment) followed by a select in a situation where two queries happen at near the same time the selects seem to return the same number. So I am guessing that something like update > update > select > select is happening.
I miss labeled this as SQL Server 2005. I am actually working with Server 2000. So the output clause does not work (is not in that version).
BEGIN TRANSACTION
UPDATE Table SET Last=(Last+1) WHERE ID=someid;
SELECT * FROM Table WHERE ID=someid;
COMMIT TRANSACTION
BEGIN TRAN
UPDATE ...
SELECT...
COMMIT
Should do it even at the default transaction isolation level of read committed.
You could also use the OUTPUT clause to get the row directly back after the update. Example of this
UPDATE <YourTable>
SET ...
OUTPUT INSERTED.*
WHERE ...