I am using SimpleJdbcTemplate batchUpdate method to do batch inserts and updates. Currently since I do not know if it is an insert or update I query the database first. Is there a better way to do this ?
No - not really.
But an alternative scheme you might consider is to do like some banks: Do only INSERTs. Then you use proper SELECT statements to select only the most recent version of each row.
Related
Lets suppose I created one table--
Create table t1 (aa varchar2(5),bb varchar2(5),cc varchar2(5));
Inserted values in it--
insert into T1 values ('a','b','c');
commit;
Now in one scenario, if i wanted to update all columns with same value then I am doing by this way--
UPDATE T1 SET AA='x',BB='x',CC='x';
Is there any another way by which this update task can be accomplished considering in real time there may be quite large number of columns and all has to be updated with same value in one go?
I am using Oracle 11.2.0.1.0 - 64bit Production
Note: Usually there are very less any scenarios where same values are being updated for all columns. But for example consider a school database and a good student scores 10/10 marks in all subjects. :-)
Thanks.
There is no way to do it in pure SQL. You must list down all the columns explicitly in the UPDATE statement.
And, believe me it is not a difficult task using a good text editor. Using the metadata you could get the list of column names in few seconds, all you need to do is prepare the SQL statement as per the syntax.
If you really want to do it dynamically, then you need to do it in PL/SQL and (ab)use EXECUTE IMMEDIATE. I would personally not suggest it unless you are just doing it for learning purpose.
You could try this:
UPDATE T1 SET AA='x',BB=AA,CC=AA;
Long time user, first time "asker".
I am attempt to construct an Oracle procedure and/or trigger that will compare two tables with the MINUS operation and then insert any resulting rows into another table. I understand how to do the query in standard SQL, but I am having trouble coming up with an efficient way to do this using PL/SQL.
Admittedly, I am very new to Oracle and pretty green with SQL in general. This may be a silly way to go about accomplishing my goal, so allow me to explain what I am attempting to do.
I need to create some sort of alert that will be triggered when the V_$PARAMETER view is changed. Apparently triggers can not respond to changes to view but, instead, can only replace actions on views...which I do not wish to do. So, what I did was create a table that to mirror that view to essentially save it as a "snapshot".
create table mirror_v_$parameter as select * from v_$parameter;
Then, I attempted to make a procedure that would minus these two so that, whenever a change is made to v_$parameter, it will return the difference between the snapshot, mirror_v_$parameter. I trying to create a cursor with the command:
select * from v_$parameter minus select * from mirror_v_$parameter;
to be used inside a procedure, so that it could be used to fetch any returned rows and insert them into another table called alerts_v_$parameter. The intent being that, when something is added to the "alert" table, a trigger can be used to somehow (haven't gotten this far yet) notify my team that there has been a change to the v_$parameter table, and that they can refer to alerts_v_$parameter to see what has been change. I would use some kind of script to run this procedure at a regular interval. And maybe, some day down the line when I understand all this better, manipulate what goes into the alerts_v_$parameter table so that it provides better information such as specifically what column was changed, what was its previous value, etc.
Any advice or pointers?
Thank you for taking the time to read this. Any thoughts will be very appreciated.
I would create a table based on the exact structure of v_$parameter with an additional timestamp column for "last_update", and periodically (via DBMS_Scheduler) merge into it any changes from the real v_$parameter table and capture the timestamp of any detected change.
You might also populate a history table at the same time, either using triggers on update of your table or with SQL.
PL/SQL is unlikely to be required, except as a procedural wrapper to the SQL code.
Examples of Merge are in the documentation here: http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_9016.htm#SQLRF01606
select max(Key) from MyTable with(nolock)
I have this T-SQL statement but need to use one statement for both SQL Server and Oracle as well, of course the “with (nolock)” is not recognised by Oracle. Is there a way having this statement that will run on both databases. By either an Oracle ignoring the “with (nolock)” or only Sqlserver using this part of the statement or a way or coded that both with understand.
The reason why I am using No lock is because multiple users are accessing the same table and I need to find the max value during the transactions.
Oracle does things a bit differently so I do not have to worry about table locks.
Your queries are doing different things. What are the semantics of the query supposed to be? Is it supposed to return max(Key) including the effect of uncommitted transactions as your SQL Server version indicates? If so
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
select max(Key)
from MyTable;
Is the same semantics. The syntax should work fine on both AFAIK.
If instead you want the last committed max(Key) you would need to change the SQL Server database to use read committed snapshot isolation by default so it behaves more similarly to Oracle. Or alternatively you could achieve similar semantics with ROWLOCK,READPAST hints but then you are back to needing two different queries.
Using Entity Framework and Oracle DB, I would like to
insert into tablename (datetimefield, numericfield) VALUES (sysdate, 545)
How to do that without using SQL code directly?
Its not possible to set it directly using the entity framework as part of the update. For inserts you coud set a default value on the table and leave it null. You could also expose an sp that updates the date to the entity framework, and call it, but that could cause many round trips.
You could also use a trigger.
If you work with dotConnect for Oracle, you can use this solution.
Devart Team
I think this question has been done before, but I don't find a clear answer.
I have migrated SQl Server 2005 database to oracle 11. I am using subsonic 2.1. I have manged to create all the data layer classes, and generates everything well. But the problem turns up when I try to make an insert in the database: Oracle does not have autoincrement in the primary key unless you define a sequence and a trigger. In consequence, Subsonic defines all the Insert methods in the controller with the id column. Is there a way to avoid subsonic not generate Insert methods with the id column, which I am going to generate using a trigger and a sequence?
Thanks a lot
SToledo
UPDATE
I finally did a horrible hack (I feel ashamed) in Subsonic 2.1 source code. I did modify OracleDataProvider to set id-named columns to be autoincrement to true. Then, the template will behave as I expect. I know is a terrible hack, but it works for me.
Thanks for your help guys.
Don't know about Subsonic, but if number of tables is relatively small, you can modify BEFORE-INSERT trigger to disable nullity check:
CREATE OR REPLACE TRIGGER trig_BI
BEFORE INSERT
ON tab_name
FOR EACH ROW
BEGIN
--IF :NEW.key_column IS NULL
--THEN
SELECT tab_seq.NEXTVAL INTO :NEW.key_column FROM DUAL;
--END IF;
END;