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Apologies for the shouting but this is important.
When answering a question please:
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Insults, slap-downs and sarcasm aren't welcome. Let's work to help developers, not make them feel stupid.
cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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For those new to message boards please try to follow a few simple rules when posting your question.- Choose the correct forum for your message. Posting a VB.NET question in the C++ forum will end in tears.
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cheers,
Chris Maunder
The Code Project Co-founder
Microsoft C++ MVP
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Hi Sir,
I try to query record from Firebird where to get record today only with this statement :
<pre>SELECT * FROM EVENT WHERE EVENTDATE >= CAST('NOW' AS DATE) AND EVENTMSG ='Access Granted'
ORDER BY EVENTDATE
Unfortunately the record appear today record and beyond ( next day upward). Can anyone help me to get record by today only.
Tq in advance.
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WHERE EVENTDATE >= CAST('NOW' AS DATE)
Your WHERE clause tells it to select records where the date is greater than or equal to today. Change it to equal only.
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Be aware that if your date is stored as a datetime (almost certainly is) you are going to have to get a range for the day + time.
The => you are using is a kludge to get that range.
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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create table PendingQueue (
id int not null,
DueTime datetime not null,
Payload varbinary(max),
cnstraint pk_pending_id nonclustered primary key(id));
create clustered index cdxPendingQueue on PendingQueue (DueTime);
go
create procedure usp_enqueuePending
@dueTime datetime,
@payload varbinary(max)
as
set nocount on;
insert into PendingQueue (DueTime, Payload)
values (@dueTime, @payload);
go
create procedure usp_dequeuePending
@batchsize int = 100,
@retryseconds int = 600
as
set nocount on;
declare @now datetime;
set @now = getutcdate();
with cte as (
select top(@batchsize)
id,
DueTime,
Payload
from PendingQueue with (rowlock, readpast)
where DueTime < @now
order by DueTime)
update cte
set DueTime = dateadd(seconds, @retryseconds, DueTime)
output deleted.Payload, deleted.id;
go
Specially see this line
set DueTime = dateadd(seconds, @retryseconds, DueTime)
How this line instruct sql server to retry the update data again after 10 minute if fail to update data first time. this is not clear to me. please some one explain if you understand properly. thanks
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It doesn't. It simply updates the DueTime column in the PendingQueue table, and returns the Payload and id columns of the affected rows.
There must be some other code which processes and removes the record from the PendingQueue table which you haven't shown.
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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I have some confusion about lock (ROWLOCK ,UPDLock AND xlock). i want to know the difference among these locks. where to use UPDLock, when to use RowLock and when Xlock with a example for better clarification.
1)
BEGIN TRANSACTION
SELECT @ID=RowID FROM MyTable WITH (ROWLOCK, XLOCK, HOLDLOCK) WHERE ID=6822
In the above sql rowlock and XLOCK both use as a result from other session records 6822 could not be read or modify. XLOCK alone is capable to lock the rows....so why one should use ROWLOCK & XLOCK together ?
if i use only xlock & HOLDLOCK then it will not serve the purpose ?
2) Tell me with example what is the difference between ROWLOCK & UPDLOCK ?
ROWLOCK prevent other session to modify data and UPDLOCK does the same thing. so what is the difference
between ROWLOCK & UPDLOCK ?
Please anyone explain these difference with example as a result at my end i can run the example code and understand.
Thanks
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Sir Thanks for your reply & link.
i read about ROWLOCK & UPDLock but still not clear. they wrote very briefly. if possible sir please discuss the difference between ROWLOCK & UPDLock hint with example.
Thanks
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I was looking for an efficient way to store "States" of entities in the DB. For example I had OrderStatus and that can be mapped to a table called Status and have the ID and the status Name be present in a join. If however I wanted to add more statuses for other Entity tables I don't want to have to create a new table for every Entity, is there a way to store all these statuses in one table? Thanks
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Richard Deeming wrote: It's a bad idea.
I , the last project I was asked to advise on was managed by a PM who was adamant that this was the "modern" way to go (I was accused of being an old fart who was stuck in the 90's). Started off as a 2 column table and the last I saw of it was a 5 column, 2 table structure.
Luckily I walked away from anything to do with the project.
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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I take this point, I restructured my schema to just have 1 table per type for the time being, I was just trying to have less tables and then ran into this anti-pattern. Thanks for the input.
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I need help resetting the values of each users in a row at once with random numbers by either button click or loading a page.
Just like a reset page or button to assign random numbers to each users without repeating at once.
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You most likely need to use a set of UPDATE statements in order to use different random values.
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I need a real-time database for inserting at least 500fields per second. (I have been selected TimeScaleDB (Postgresql Extension) for my purpose, currently). So, the matrix of the table will be 500(Fields)x86400(Rows).
This means that for a 500 double-precision field it will be around 500*8bytes=4000bytes which for 86400rows it will be 345,600,000bytes (345.6M).
I know a software which it is recording the same structure of data and the final daily volume of its database is only 84M~85M. Its Extension is *.tag so, i think it is a DataFlex database. It is not a free database and i also never used it.
Question:
1- Which free database is the best to use for real-time data storing and querying (at the moment of storing) based on your experience or knowledge?
2- Is there any database to have such a volume or even less for this size of data?
Thank you for your Help.
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But Its Volume Will Be The Same As PostgreSQL!
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Why are you concerned about sizes? Disk space is cheap.
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For one year the size will be 120GB for Postgresql but for the mentioned DBS will be only 30GB. it is a great difference (one fourth).
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That would mean the other database is storing the data compressed.
That's obviously something you can do in many databases, but it might add performance issues.
Wrong is evil and must be defeated. - Jeff Ello
Never stop dreaming - Freddie Kruger
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What is wrong with MySQL[^]
Never underestimate the power of human stupidity -
RAH
I'm old. I know stuff - JSOP
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