So this is the problem, I have a Oracle table, just a normal table with let's say 300 rows of data.
I need to figure out how that data looked like at least 100 days before, who made changes and timestamp would be nice also.
Thing is, I do have a schedule backup, but I believe someone changed data and removed backup, so I am trying to find out this change over system records.
I did google this and for results I got now, I didn't got what I needed.
select * from dba_hist_sqltext - it gives me results for current session only
SELECT SCN_TO_TIMESTAMP(ORA_ROWSCN) - specified number is not a valid system change number
Oracle SQL info -
Java(TM) Platform 1.7.0_51
Oracle IDE 4.0.0.13.80
Versioning Support 4.0.0.13.80
Do you guys have any other idea?
Thank you in advance
You may use flashback: Using Oracle Flashback Technology
With that, you can query using the AS OF TIMESTAMP clause, like this:
SELECT * FROM yourtable
AS OF TIMESTAMP TO_TIMESTAMP('2004-04-04 09:30:00', 'YYYY-MM-DD HH:MI:SS');
This has to be enabled though, and there is a certain (configurable) size limit, so there is no guarantee that you can still query those records of 100 days ago. On a busy database the history may go back only a couple of minutes.
Related
We have a web application which we store a date from the user. The date is stored on an Oracle 19c database as a date field.
The problem we have is that when we select the date it's coming with different hours, like it's taking into account the timezone or something. So, for example one person can see the date 2021-05-20T13:00:00Z while another somewhere else can see 2021-05-20T12:00:00Z.
Is there a way to prevent this behavior, and have everybody get the same date and time?
Update
Most likely the problem resides in Oracle Apex, not Oracle database!
We use a very old version of Apex, 1.x it seems so maybe this problem doesn't happen on newer versions.
That is often problem when you use, for example, java.util.Timezone,java.sql.Date or java.util.Date type in java instead of oracle.sql.Date
I'm using SQL Link server for fetching data from MariaDB.
But I fetching issue with slowness when i used MariaDB from link server.
I used below scenarios to fetch result (also describe time taken by query)
Please suggest if you have any solutions.
Total number of row in patient table : 62520
SELECT count(1) FROM [MariaDB]...[webimslt.Patient] -- 2.6 second
SELECT * FROM OPENQUERY([MariaDB], 'select count(1) from webimslt.patient') -- 47ms
SELECT * FROM OPENQUERY([MariaDB], 'select * from webimslt.patient') -- 20 second
This isn’t really a fair comparison...
SELECT COUNT(1) is only returning a single number and will probably be using an index to count rows.
SELECT * is returning ALL data from the table.
Returning data is an expensive (slow) process, so it will obviously take time to return your data. Then there is the question of data transfer, are the servers connected using a high speed connection? That is also a factor in this. It will never be as fast to query over a linked server as it is to query your database directly.
How can you improve the speed? I would start by only returning the data you need by specifying the columns and adding a where clause. After that, you can probably use indexes in Maria to try to speed things up.
When using vsql, I would like to see how long a query took to run once it completes. For example when i run:
select count(distinct key) from schema.table;
I would like to see an output like:
5678
(1 row)
total query time: 55 seconds.
If this is not possible, is there another way to measure query time?
In vsql type:
\timing
and then hit Enter. You'll like what you'll see :-)
Repeating that will turn it off.
Regarding the other part of your question:
is there another way to measure query time?
Vertica can log a history of all queries executed on the cluster which is another source of query time. Before 6.0 the relevant system table was QUERY_REPO, starting with 6.0 it is QUERY_REQUESTS.
Assuming you're on 6.0 or higher, QUERY_REQUESTS.REQUEST_DURATION_MS will give you the query duration in milliseconds.
Example of how you might use QUERY_REQUESTS:
select *
from query_requests
where request_type = 'QUERY'
and user_name = 'dbadmin'
and start_timestamp >= CURRENT_DATE
and request ilike 'select%from%schema.table%'
order by start_timestamp;
The QUERY_PROFILES.QUERY_DURATION_US and RESOURCE_ACQUISITIONS.DURATION_MS columns may also be of interest to you. Here are the short descriptions of those tables in case you're not already familiar:
RESOURCE_ACQUISITIONS - Retains information about resources (memory, open file handles, threads) acquired by each running request for each resource pool in the system.
QUERY_PROFILES - Provides information about queries that have run.
I'm not sure how to enable that in vsql or if that's possible. But you could get that information from a script.
Here's the psuedocode (I used to use perl):
print time
system("vsql -c 'select * from table'");
print time
Or put time into a variable and do some subtraction.
The other option is to use some tool like Toad to connect to Vertica instead of using vsql.
I have a database with many tables that get used, and many tables that are no longer used. While I could sort through each table manually to see if they are still in use, that would be a cumbersome task. Is there any software/hidden feature that can be used on a SQL Server/Oracle database that would return information like "Tables x,y,z have not been used in the past month" "Tables a,b,c have been used 17 times today"? Or possibly a way to sort tables by "Date Last Modified/Selected From"?
Or is there a better way to go about doing this? Thanks
edit: I found a "modify_date" column when executing "SELECT * FROM sys.tables ORDER BY modify_date desc", but this seems to only keep track of modifications to the table's structure, not its contents.
replace spt_values with the tablename you are interested in, the query will give the the last time it was used and what it was used by
From here: Finding Out How Many Times A Table Is Being Used In Ad Hoc Or Procedure Calls In SQL Server 2005 And 2008
SELECT * FROM(SELECT COALESCE(OBJECT_NAME(s2.objectid),'Ad-Hoc') AS ProcName,execution_count,
(SELECT TOP 1 SUBSTRING(s2.TEXT,statement_start_offset / 2+1 ,
( (CASE WHEN statement_end_offset = -1
THEN (LEN(CONVERT(NVARCHAR(MAX),s2.TEXT)) * 2)
ELSE statement_end_offset END) - statement_start_offset) / 2+1)) AS sql_statement,
last_execution_time
FROM sys.dm_exec_query_stats AS s1
CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS s2 ) x
WHERE sql_statement like '%spt_values%' -- replace here
AND sql_statement NOT like 'SELECT * FROM(SELECT coalesce(object_name(s2.objectid)%'
ORDER BY execution_count DESC
Keep in mind that if you restart the box, this will be cleared out
In Oracle you can use the ASH (Active Session History) to find info about SQL that was used. You can also perform code coverage tests with the Hierarchical profiler, where you can find which parts of the stored procedures is used or not used.
If you wonder about the updates on table data, you can also use DBA_TAB_MODIFICATIONS. This shows how many inserts, updates, deletes are done on a table or table partition. As soon as new object statistics are generated, the row for the specified table is removed from DBA_TAB_MODIFICATIONS. You still have help here, since you could also have a peek in the table statistics history. This does not show anything about tables that are queried only. If you really need to know about this, you are to use the ASH.
Note, for both ASH and statistics history access, you do need the diagnostics or tuning pack license. (normally you would want this anyway).
If you use trigger you can detect update insert or delete on table.
Access is problably more difficult.
I use a combination of static analysis in the metadata to determine tables/columns which have no dependencies and runtime traces in SQL Server to see what activity is happening.
Some more queries that might be useful for you.
select * from sys.dm_db_index_usage_stats
select * from sys.dm_db_index_operational_stats(db_id(),NULL,NULL,NULL)
select * from sys.sql_expression_dependencies /*SQL Server 2008 only*/
The difference betweeen what the first 2 DMVs report is explained well in this blog post.
Ed Elliott's open source tool, SQL Cover, is a good bet and has built-in support for the popular unit testing tool, tSQLt.
I am faced with a peculiar requirement which is as follows:
A network-intensive operation is triggered to a server by multiple clients, through a web-interface. However, only one operation is allowed at a time, and hence an entry(tuple) is made in an SQL table to indicate that the operation is in progress. Once the operation is complete (irrespective of success or failure), the appropriate result is displayed back to the client(s), and the corresponding tuple is removed from the SQL table.
Since the operation is network-intensive, a scenario where the operation needs to be "considered" to be cancelled, after some timeout (10 minutes) has to be introduced.
Is there ANY way the lifetime of a row in SQL be associated with a timeout value, so that is is deleted after certain time? My application is primarily written in Java 1.5 and EJB 3.0, using JPA/Hibernate to access Oracle 10g DB engine.
Thanks in advance.
Regards,
Nagendra U M
I would suggest that you try using a timestamp column containing the start time of the task.
A before trigger can be then made to delete the old column before a new one is inserted if the task timed out.
If you want to have multiple tasks with different timeouts, you can even add a column with the timeout in seconds. Just code your trigger accordingly.
I don't know that Oracle has this kind of facility but I think no db engine have this.
If you want to do it at DB level,
you must have a datetime column, e.g.; 'CreatedDate' in
table. This column will have
datetime when record was created.
Write a procedure and put it in a
schedule job. This job will run after every 10 minutes and remove the 10 minutes old records. The query will be like
this.
T-SQL: Please convert it according to your db engine.
DELETE FROM yourtable WHERE CreatedDate < DATEADD(mi, -10, GETDATE())
This will delete all records older than 10 minutes from table.
This is just to give you idea of schedule job. It is in SQL Server. I don't know about Oracle
step_by_step_guide_to_add_a_sql_job_in_sql_server_2005
It sounds like you're implementing a mutex using the database, take a look at this question and see if it helps? Sounds like transactional access to a flag table will solve this for you, as long as you catch both success & failure states in your server code.