Always read the error message - Syntax Error, permission violation, or nonspecific Reviews another error
There is either:
An error in the sql - you can check this by running the sql in isolation.
A permission issue - harder to track, I would test this by creating a simple SSIS package and try to run it from your code.
Non specific error - eliminate the first two possibilities then look into this.
“That which can be asserted without evidence, can be dismissed without evidence.”
What's the version / localization of your SQL Server?
I tried it with SQL Server 10.0.5500, German localized Management studio. I adjusted the date format of your query, and tested it. And it worked as it was expected to work - I cannot reproduce your bug.
Msg 1823, Level 16, State 2, Line 1
A database snapshot cannot be created because it failed to start.
Msg 7928, Level 16, State 1, Line 1
The database snapshot for online checks could not be created.
Either the reason is given in a previous error or one of the underlying volumes
does not support sparse files or alternate streams. Attempting to get exclusive
access to run checks offline.
Assuming that one person can have multiple payments, an INNER JOIN will return a record for every payment over two months old, regardless of whether the person has paid within the last two months.
What you need to do is find the person records which don't have a payment record within the last two months. To do that, you can use a Not Exists filter:
DECLARE @Today date = GetUtcDate();
DECLARE @CutoffDate date = DateAdd(month, -2, @Today);
WHERE payment.national_number = person.national_number
And payment.payment_date > @CutoffDate
"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer
I have been searching all day to find a better answer to my question but those I found was useful
but do not critically analyse my question.
I am building a chat room using php, mysql, jquery and ajax.
The target group members are 3000 people who will frequently
chat every day, so I am expecting like one million messages a day.
The chat room is open to all the members, that means
every member has the same priviledge to send and view
In this case, every member has the permission to delete messages whether sent by him or different members,
however deleted messages should not affect other users. I wouldnt also keep messages for more than two days,
meaning every sent message should be deleted after two days.
Below are the sample tables that represents the logics above
Now, if I am to implement the schema above, it means that every single sent message has to do 3000 inserts into the
recipient table and one insert into the messages table. This also means that if there are 50 sent messages within 1 minute there would be more
inserts within the one minute. At the same time 3000 people are viewing the messages. Awwsh! more work load on the database within that minute.
Please is there a way to handle this, scalability and performance wise?
Any idea is appreciated. Thanks.
Last Visit: 31-Dec-99 19:00 Last Update: 28-Dec-14 1:26