I need help with a query that does the following:
Start from the newest record and go downwards to the older records.
It needs to be ordered by created_at time.
If there are new records in the database by created_at time, retrive them but do not get records I already got from step 1.
I want to only get only 16 records at a time. That number can change later.
Do not retrive records I already sent from a previous time.
Also just to let you know, this is started via $.ajax.
Reason for this is because I am getting new + old records real-time to be sent to the client. Think something like like user starts off visiting the website and it gets the current records starting with new ones. Then the user can go get older records, but at the same request, it also retrieves the brand new records. With a twist of only 16 records at a time.
Do I make sense?
This is what I currently have for code:
RssEntry.includes(:RssItem).where("rss_items.rss_id in (?) AND (rss_entries.id < ? OR rss_entries.created_at > ?)", rssids, lid, time).order("rss_entries.id DESC").limit(16)
lid = last lowest id from those records
rssids = ids from where to get the records
time = last time it did the records call
That code above is only the beginning. I now need help to make sure it fits my requirements above.
UPDATE 1
Ok, so I managed to do what I wanted but in 2 sql queries. I really don't think it is possible to do what I want in one sql query.
Any help is greatly appreciated.
Thanks.
Firstly, use scopes to get what you want:
class RssEntry < ActiveRecord::Base
scope :with_items, includes(:RssItem)
scope :newer_first, order("rss_entries.created_at DESC")
def self.in(args)
where(id: args)
end
def self.since(time)
where('rss_entries.created_at > ?', time)
end
end
then
RssEntry.with_items.in(rssids).since(time).offset(lid).limit(16).newer_first
It should work as expected.
Related
I have a view that lists employee (EmpID), request number (ReqNo), date request was opened (OpenDate) and the date it was moved to the next step in the process (AssignDate). What I am trying to do is get an average of the daily queue size. If EmpID 001 has 20 requests on 1/1/13, then has 24 on 1/2/13, 21 on 1/3/13 the average over 3 days should be 21.66, rounded up to 22. I have the following view:
CREATE VIEW EmpReqs
AS
SELECT [EmpID], [OpenDate], [AssignDate], [ReqID]
FROM [Metrics].[dbo].[Assignments]
WHERE OpenDate BETWEEN '01/01/2013' AND '12/31/2013' AND
[EmpID] IS NOT NULL AND
[ReqNo] NOT LIKE 'M%'
I then wrote a query to pull individual employee's queues per day:
/* First attempt to generate daily queue #s */
SELECT * FROM BLReqs
WHERE [BusLiaison] LIKE 'PN' AND
[OpenDate] <= '11/15/2013' AND
[AssignDate] > '11/15/2013'
Because no one has attempted to pull this information before, I have no way of verifying how accurate the above is. I tried using current dates, since I can see those in our database to compare but the code doesn't work, nothing is returned when I change the dates to 2014 and run my query.
What is the easiest way to verify that my code is correct, short of manually counting a day's queue?
Can anyone see any issues with the above scripts?
Is there a way to get the above code to work with current dates?
This question is really hard to answer because it is kind of broad and has little information at the same time. I'll try anyway:
Because no one has attempted to pull this information before, I have
no way of verifying how accurate the above is.
Try checking the result of this query for a few sampled dates.
I tried using current dates, since I can see those in our database to
compare but the code doesn't work, nothing is returned when I change
the dates to 2014 and run my query.
So clearly, the query is not working. You should probably find out why. Run the query for a date of which you know that it should return results but doesn't. Remove conditions one by one to see which one is incorrectly removing all rows. This should be enough to identify the bug.
Can anyone see any issues with the above scripts?
No, looks fine. A very simple query. That's why I said that we have too little information. There is some key piece of information missing that allows us to find the bug.
Is there a way to get the above code to work with current dates?
Stop staring at the code and hoping for a revelation. Debug it. Experiment.
Hello I need a SQL query statement that gets me rows 'start' to 'finish'.
For example:
A website with many items where page 1 selects only items 1-10, page 2 has 11-20 and so on.
I know how to do this with Microsoft SQL Server and MySQL but I need an implementation that is platform independent. :/
I have an Increment line for IDs but deleting in-between will mess the result when I select via
WHERE ID > number AND ID < othernumber
of course
Is this possible without fetching the whole database to a ResultSet?
I think your safest bet would be to use the BETWEEN operator. I believe it works across Oracle/MySQL/MSSQL.
WHERE ID BETWEEN number AND othernumber
Concerning your comment " I was just think for the case when first 100 IDs are gone I'll have to check further until there is something to fetch", you might wanna consider NOT actually ever deleting stuff from your database but to add a flag like "active" or something like that to your tables so you can avoid situations like the one you're now trying to avoid. The alternative is where you are now, having to find the max and min rows in a filter
I have a weekly view of projects. For each project I'm grabbing the first record for each day of the week. It's important to me to always get the first record for that day, and know which weekdays have no records. Right now I'm doing this with a separate SQL string for each project + day of week combo in a nested for loop.
This feels wrong. It seems like I should be able to get this with ActiveRecord / SQL via Group By and Limit, and use Ruby/Rails to process the results. Is this possible?
Thanks in advance.
– David
Does that do the job? (Using MySQL)
#projects = []
for day in 1..7
#projects.push Project.where("DAYOFWEEK(project_date) = ?", day).where(:project_date => Time.now.all_week).order('project_date desc').first
end
#Time.now.all_week assumes you're working with Rails 3.2
Take a look at DATEOFWEEK() in MySQL docs
You can test with
for pj in #project
p pj.project_date if pj.project_date #nil if no project found
end
(I tried posting this to the CFWheels Google Group (twice), but for some reason my message never appears. Is that list moderated?)
Here's my problem: I'm working on a social networking app in CF on Wheels, not too dissimilar from the one we're all familiar with in Chris Peters's awesome tutorials. In mine, though, I'm required to display the most recent status message in the user directory. I've got a User model with hasMany("statuses") and a Status model with belongsTo("user"). So here's the code I started with:
users = model("user").findAll(include="userprofile, statuses");
This of course returns one record for every status message in the statuses table. Massive overkill. So next I try:
users = model("user").findAll(include="userprofile, statuses", group="users.id");
Getting closer, but now we're getting the first status record for each user (the lowest status.id), when I want to select for the most recent status. I think in straight SQL I would use a subquery to reorder the statuses first, but that's not available to me in the Wheels ORM. So is there another clean way to achieve this, or will I have to drag a huge query result or object the statuses into my CFML and then filter them out while I loop?
You can grab the most recent status using a calculated property:
// models/User.cfc
function init() {
property(
name="mostRecentStatusMessage",
sql="SELECT message FROM statuses WHERE userid = users.id ORDER BY createdat DESC LIMIT 1,1"
);
}
Of course, the syntax of the SELECT statement will depend on your RDBMS, but that should get you started.
The downside is that you'll need to create a calculated property for each column that you need available in your query.
The other option is to create a method in your model and write custom SQL in <cfquery> tags. That way is perfectly valid as well.
I don't know your exact DB schema, but shouldn't your findAll() look more like something such as this:
statuses = model("status").findAll(include="userprofile(user)", where="userid = users.id");
That should get all statuses from a specific user...or is it that you need it for all users? I'm finding your question a little tricky to work out. What is it you're exactly trying to get returned?
I made a SQL query to update registers on a table. The table has about 15 million registers. The update statement is like:
UPDATE temp_conafe
set apoyo = trim(apoyo)
where cve_status like '%APOYO%';
I keep checking the field v$transaction.used_ured to see if the query is rolling forward or backwards but when the number of records reach to more than 15 millions the query starts rolling backwards.
How do I get the update to complete successfully?
I'm not the DBA, just a programmer, but I can't keep developing till that thing updates my registers.
It looks as if your transaction is to big. Try to add another limiting clause in the where. If you have a Id field you can add something like this:
where cve_status like '%APOYO%'
AND id > 1 AND id < 100000
You need to run it multiple times an change the range accordingly. If this is not an option you have to talk to your DBA and ask him to give you more resources.