There are so many work tables which are created some many days back and not dropped yet and tempdb was stocked.
Regards
Related
I am using a SQL database and MS Access 2019 as the front end. The SQL database tables are linked to the Access db using an ODBC connection.
All my queries (they have multiple joined linked tables) run just fine, but as soon as I add a join to a table stored in the Access app (for example, a small table just for mapping values) the query will slow to a crawl. Doesn't matter if the joined fields are indexed or what type of join I'm using.
If anyone has seen this behaviour and found a solution I would much appreciate hearing it.
Joining tables from two separate databases requires the client app to retrieve both tables in their entirety in order to determine the rows needed. That's why it's slow.
If your Access table is small, try using a stored procedure on the SQL side with the data from Access moved to a temporary table. (Or better yet, move the Access table to SQL).
So I have a summary i need to return to the end user application.
It should accept 3 parameters DateType, StartDate, EndDate.
Date Type will determine the date field I use to filter the data.
The way i accomplished this was putting all the IDs of the records for a datetype into a TEMP table and then joining my summary to the list of IDs.
This worked fine when running on the query on the SQL server that houses the data.
However, that is a replicated server, so when I compiled to a stored proc that would be on the server with the rest of the application data, it slowed the query down. IE 2 seconds vs 50 seconds.
I think the cross join from the temp table that is created on the SQL server then joining to the tables on the replciation server, is causing the slow down.
Are there any methods or techniques that I can use to get around this and build this all in one stored procedure?
If I create 3 stored procedures with their own date range, then they are fast again. However, this means maintaining multiple stored procs for the same thing.
First off, if you are running a version of SQL Server older than 2012 SP1, one problem is that users who aren't allowed to run DBCC SHOW_STATISTICS (which is most users who aren't sysadmins, see the "Permissions" section in the documentation) don't get access to statistics on remote tables. This can severely cripple the optimizer's ability to generate a good execution plan. Upgrading SQL Server or granting more permissions can help there.
If your query involves filtering or joining on a character column, make sure the remote server is flagged in the linked server options as "collation compatible". If this option is off, SQL Server can't assume strings can be compared across the servers and it will start pumping entire tables up and down just to make sure the data ends up where the comparison has to be made.
If the execution plan is as good as it gets and it's still not good enough, one general (lame) technique is to transfer all data locally first (SELECT * INTO #localtable FROM remote.db.schema.table), then run the query as a non-distributed query. Obviously, in order for this to work, the remote table cannot be "too big" and in some cases this actually has worse performance, depending on how many rows are involved. But it's always worth considering, because the optimizer does a better job with local tables.
Another approach that avoids pulling tables together across servers is packing up data in parameters to remote stored procedure calls. Entire tables can be passed as XML through an NVARCHAR(MAX), since neither XML columns nor table-valued parameters are supported in distributed queries. The basic idea is the same: avoid the need for the the optimizer to figure out an efficient distributed query. The best approach greatly depends on your data and your query, obviously.
I have a PostgreSQL database that stores real-time data from sensors in a specific table (every 30sec).
What I want to do, is to get periodically the data from the remote PostgreSQL database (for instance every 30sec) and store them in SQL Server 2005 to manipulate them locally. I don't care about having the two databases with duplicate tables. Actually this is what I want to achieve!
So far, I have as Linked Server the PostgreSQL to SQL Server and I can query and retrieve the sensor data. However, I prefer to store them in my SQL Server for performance reasons.
Solution so far:
Make select openquery statements with the linked PostgreSQL and insert the results to my table in SQL Server. Repeat this periodically and store fresh data only (e.g. with a larger timestamp).
I assume that my proposed solution is not ideal. I want to know what are the best practices to achieve this synchronization between the two databases.
Thank you in advance!
If you don't want to write your own code(implementations) to do that you can use SymmetricDS to synch the table from postgreSQL to MSSQL .
Excuse me but I am very new at learning to use oracle and sql.
I was given a bat file by my teacher that runs an sql to setup a database. The sql basically just drops 5 tables and recreates them with data.
What I don't understand is why I am seeing tons of other tables (that came with oracle?)
Why am I seeing all of these tables http://i.imgur.com/AvliJ.jpg
the only tables that are supposed to be created are
REP
CUSTOMER
ORDERS
PART
ORDER_LINE
Is there a way to only display those?
The other tables are tables Oracle uses.
Whether you see them or not depends on your permissions in the database. Ask your teacher to show you how to reduce your permissions so that you can only see the five tables your supposed to or look at the Oracle documentation here User Admin.
ETA : Be careful if you do start messing with permissions.
I need to quickly implement a read-only database containing data pulled from two identically structured live databases.
The live dbs are actually company dbs from a Dynamics accounting system so I'm happy for any Dynamics specific advice but this is mostly a SQL question. It's a fairly old version of Dynamics from before Great Plains was acquired by Microsoft. This is on SQL Server 2000.
We have reports and applications which access the Dynamics data. These apps are designed to look at one company db. Now we need to add another. It's appropriate that most of these reports and apps see combined data. They don't really care which company an order or invoice exists in. They only look at a small number of the tables.
It seems to me that the simplest solution is to create a reports only db with combined data. Preferably, we need an efficient way to update this db with changes several times a day.
I'm a developer, not a db expert but here's my plan:
Create the combined reporting db with the required tables initially with the same table structure as the live dbs.
All Dynamics tables seem to have an int identity column called DEX_ROW_ID. I'm not sure what it's used for, (it's not indexed) but that seems like the obvious generic way to uniquely identify rows. On the reporting db I will change it to a normal int (not an identity). I will create a unique index on DEX_ROW_ID in all dbs.
Dynamics does not have timestamps so I will add a timestamp column to tables in the live dbs and a corresponding binary(8) column in the reporting db. I'm assuming and hoping that Dynamics won't be upset by the additional index and column.
Add an int CompanyId column to the reporting db tables and add it to the end of any unique indexes. Most data will be naturally unique even without that. ie, order and invoice numbers etc will be different for the two live dbs. We may need to make some minor changes to the applications but I'm not expecting to do much other than point them to the new reporting db.
Assuming my reporting db is called Reports, the live dbs are Live1 and Live2, the timestamp column is called TS and all dbs are on the same server ... here's my first attempt at an update script for copying the changes in one table called MyTable in Live1 to the reporting db.
USE Reports
CREATE TABLE #Changes
(
ReportId int,
LiveId int
)
/* Collect in a temp table the ids or rows which have been deleted or changed
in the live db L.DEX_ROW_ID will be null if the row has been deleted */
INSERT INTO #Changes
SELECT R.DEX_ROW_ID, L.DEX_ROW_ID
FROM MyTable R LEFT OUTER JOIN Live1.dbo.MyTable L ON L.DEX_ROW_ID = R.DEX_ROW_ID
WHERE R.CompanyId = 1 AND L.DEX_ROW_ID IS NULL OR L.TS <> R.TS
/* Delete rows that have been deleted or changed on the live db
I wonder if using join syntax would run better than the subquery. */
DELETE FROM MyTable
WHERE CompanyId = 1 AND DEX_ROW_ID IN (SELECT ReportId FROM #Changes)
/* Recopy rows that have changed in the live db */
INSERT INTO MyTable
SELECT 1 AS CompanyId, * FROM Live1.dbo.MyTable L
WHERE L.DEX_ROW_ID IN (SELECT ReportId FROM #Changes WHERE LiveId IS NOT NULL)
/* Copy the rows that are new in the live db */
INSERT INTO MyTable
SELECT 1 AS CompanyId, * FROM Live1.dbo.MyTable
WHERE DEX_ROW_ID > (SELECT MAX(DEX_ROW_ID) FROM MyTable WHERE CompanyId = 1)
Then do the same for the Live2 db. Repeat for every table in Reports. I know I should use a parameter #CompanyId instead of the literal but I can't do that for the live db name some I might generate these dynamically with a C# program or something.
I'm looking for any advice, suggestions or critique on what I'm doing here. I know it won't be atomic. Things could be happening on the live db while this script runs. I think we can live with that. We'll probably do a full copy either nightly or weekly when nothing is happening on the live dbs.
We need to favor performance over elegance or perfection. Some initial testing has the first query with the TS comparisons running at about 30 seconds for the biggest table so I'm optimistic that this is going to work but I'd also like to know if I'm missing something obvious or not seeing the forest for the trees.
We don't really want to deal with log files on the reporting db. Can we just set that to simple recovery model and forget about logs?
Thanks
I think there are a couple open questions here.
Do you need these reports to be near-real-time? Or is this this sort of reporting that could live with daily updates? But assume you need up-to-the-minute data.
Have you considered querying the databases directly and merging the data per-report on the fly? You'll have to do a lot of reporting to duplicate the effort that's going to go into designing, creating, and supporting a real-time merged replicated database.
Thirty seconds is (IMHO) unacceptable for any single query against a production database. There could be any number of tuning-related reasons for taking this long, but it at least means you're going to need serious professional SQL Server optimization resources (i.e. people). And if this is a problem for the queries for reports, it doesn't bode well for the queries to maintain a separate database for reporting.
Tuck into the back of your mind the consideration that, if you need to consolidate to a single database, it's worth considering whether you should make it an OLAP database rather than a mirror. The mirror will be quicker and easier, but the OLAP would be far more flexible and powerful in the long term; and it might be well to go the whole way from the beginning.
The last thing I'd want to do is write a custom update script. Try these bulletproof methods first:
Let's hope your production databases are backed up. Restore those backups every night to the reporting server. You can automate restores with the RESTORE command, which will work with a file on a network server.
Use SQL Server replication to push data from the live servers to the backend.
Schedule a DTS package every night to import the entire production database.
This might seem like brute force. But since you're copying a 2000-era database, brute force cannot be a problem with today's hardware. As an added advantage, these methods can be supported by a sysadmin instead of a developer.
Method 1 has the added added advantage of serving as backup verification. :)