In nodejs i want to insert data 3 different tables, if any one query fails to execute i want all the changes done by the other queries to revoke the changes in the table.
See this part of mysql package documentation: https://github.com/mysqljs/mysql#transactions
Only once you execute all 3 queries you can call connection.commit() to apply changes or connection.rollback() to revert changes as shown on the example on the link.
Related
I have a session created in my vb.net codes and running some SQL queries, there are some local temp tables like #T1, #T2 , ...
Execution process has some steps and I need to know which data changes in my local tables in each step.
Currently I use this to view the data in my code:
select * into ##T1 from #T1
I can't use sp_getbindtoken because there is no active transaction. I can not use DBCC because I don't have permission.
I can run sys.dm_exec_sessions view and therefor I have active session_id,
I also have connection Index of active sql connection
is there any way to connect to a active session and access local temp tables?
or is there any way to get those data of #T1, #T2,...?
EDIT1:
according to the comment which commented by #SeanLange
I have some temp tables as I said, and in the steps mentioned before I do some calculations on these temp tables, for tracing these calculations I need to know what happens in these steps, and I want to execute a simple select statement on these temp tables. what I wanted to do was connect to the active session created in my source code from an external project called Tracer, and perform select statements while my source is on the fly and meanwhile trace the data created in these session
You can't do it. Sorry. (at least without sa privileges).
Run your queries from within a stored procedure and add code to log whatever you need to a table, then query the log table as needed.
Execution process has some steps and I need to know which data changes in my local tables in each step.
If you have permission, you can create a trigger to do the logging for you
The database I'm working on has a trigger which calls a stored procedure which takes 42 seconds to run if I do an UPDATE using T-SQL. If I edit the row in SQL Server Management Studio, the row updates instantly. Triggers are executed in the edit window as well as on T-SQL UPDATES, aren't they?
The SQL code in the stored procedure comes back instantly if I run it directly or call it using EXEC, the only circumstances when it runs slowly are when the trigger is called by an UPDATE statement.
It depends how the trigger was set up, Triggers will only run on Update, Delete and Insert statements (Depending which of the three are chosen) On the table it is set against.
Could you give the code used to create the trigger?
These triggers run after an insert, update or delete on a table
click here for details about different type of triggers and demo for triggers
I have multiple select queries which I want to execute asynchronously.
How can I do this in oracle sql ?
I basically want to test something and so want to simulate workload so I don't really care about the result and I know I can do this in multiple threads but this is specific and so would prefer if I can do this entirely in sql. procedures are fine though.
NOTE: there are no update queries only select.
I read about nowait but am not sure how to use it in oracle.
I tried something like -
select * from foo with(nowait) where col1="something";
This is the error I got -
with(nowait)
*
ERROR at line 3:
ORA-00933: SQL command not properly ended
The Oracle info on NOWAIT says:
Specify NOWAIT if you want the database to return control to you immediately
if the specified table, partition, or table subpartition is already locked by
another user. In this case, the database returns a message indicating that the
table, partition, or subpartition is already locked by another user.
This will not do what you want.
Asynchronous queries are an application thing, not a SQL thing. For example I can open TOAD and open a dozen windows and run long queries in all of them and still open another window and run another query. I could open a dozen instances of SQLPLUS and do the same thing. Nothing in the query lets me do this, it's in the application.
I think you could use DBMS_SCHEDULER to schedule some sql or procs that execute SQL.
However this is probably not the best way to do this
There are tools for this. The best way maybe to write a procedure you can call from the web and then you can use any performance testing tool that can make a web call...its worked for me before.
You may also consider:
http://sqlmag.com/database-performance-tuning/testing-heavy-load-simulating-multiple-concurrent-operations
I have a huge sql server script which has mix of ddl, dml operations and there is a requirement to create a clean db structure (with no data). Is it possible for a transaction to skip DML scripts through some parameter or some other way.
Thanks in Advance.
Arun
Out of the box: no. But you can wrap the DML statements in your script with something like:
if ($(RUNDML) = 1)
begin
--your dml here
end
Where RUNDML is a sqlcmd variable. You'd invoke your script with differing values of RUNDML based on whether or not you wanted data in the database being built.
Alternatively, separate the DML out into another script (or scripts) so you can choose whether to run the data portion of the build or not.
I have a problem to solve which requires undo operation of each executed sql file in Oracle Database.
I execute them in an xml file with MSBuild - exec command sqlplus with log in and #*.sql.
Obviously rollback won't do, because it can't rollback already commited transaction.
I have been searching for several days and still can't find the answer. What I learned is Oracle Flashback and Point in Time Recovery. The problem is that I want the changes to be undone only for the current user i.e. if another user makes some changes at the same time then my solution performs undo only on user 'X' not 'Y'.
I found the start_scn and commit_scn in flashback_transaction_query. But does it identify only one user? What if I flashback to a given SCN? Will that undo only for me or for other users as well? I have taken out
select start_scn from flashback_transaction_query WHERE logon_user='MY_USER_NAME'
and
WHERE table_name = "MY_TABLE NAME"
and performed
FLASHBACK TO SCN"here its number"
on a chosen operation's SCN. Will that work for me?
I also found out about Point in Time Recovery but as I read it makes the whole database unavailable so other users will be unable to work with it.
So I need something that will undo a whole *.sql file.
This is possible but maybe not with the tools that you use. sqlplus can rollback your transaction, you just have to make sure auto commit isn't enabled and that your scripts only contain a single commit right before you end the sqlplus session (if you don't commit at all, sqlplus will always roll back all changes when it exits).
The problems start when you have several scripts and you want, for example, to rollback a script that you ran yesterday. This is a whole new can of worms and there is no general solution that will always work (it's part of the "merge problem" group of problems, i.e. how can you merge transactions by different users when everyone can keep transactions open for as long as they like).
It can be done but you need to carefully design your database for it, the business rules must be OK with it, etc.
To general approach would be to have a table which contains the information which rows were modified (= created,updated,deleted) by the script plus the script name plus the time when it was executed.
With this information, you can generate SQL which can undo the changes created by a script. To fill such a table, use triggers or generate your scripts in such a way that they write this information as well (note: This is probably beyond a "simple" sqlplus solution; you will have to write your own data loader for this).
Ok I solved the problem by creating a DDL and DML TRIGGER. The first one takes "extra" column (which is the DDL statement you have just entered) from v$open_cursor and inserts into my table. The second gets "undo_sql" from flashback_transaction_query which is the opposite action of your DML action - if INSERT then undo_sql is DELETE with all necessary data.
Triggers work before DELETE,INSERT (DML) on specific table and ALTER,DROP,CREATE (DDL) on specific SCHEMA or VIEW.