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  • How to combine two rows and calculate the time difference between two timestamp values in MySQL?

    - by Nadar
    I have a situation that I'm sure is quite common and it's really bothering me that I can't figure out how to do it or what to search for to find a relevant example/solution. I'm relatively new to MySQL (have been using MSSQL and PostgreSQL earlier) and every approach I can think of is blocked by some feature lacking in MySQL. I have a "log" table that simply lists many different events with their timestamp (stored as datetime type). There's lots of data and columns in the table not relevant to this problem, so lets say we have a simple table like this: CREATE TABLE log ( id INT NOT NULL AUTO_INCREMENT, name VARCHAR(16), ts DATETIME NOT NULL, eventtype VARCHAR(25), PRIMARY KEY (id) ) Let's say that some rows have an eventtype = 'start' and others have an eventtype = 'stop'. What I want to do is to somehow couple each "startrow" with each "stoprow" and find the time difference between the two (and then sum the durations per each name, but that's not where the problem lies). Each "start" event should have a corresponding "stop" event occuring at some stage later then the "start" event, but because of problems/bugs/crashed with the data collector it could be that some are missing. In that case I would like to disregard the event without a "partner". That means that given the data: foo, 2010-06-10 19:45, start foo, 2010-06-10 19:47, start foo, 2010-06-10 20:13, stop ..I would like to just disregard the 19:45 start event and not just get two result rows both using the 20:13 stop event as the stop time. I've tried to join the table with itself in different ways, but the key problems for me seems to be to find a way to correctly identify the corresponding "stop" event to the "start" event for the given "name". The problem is exactly the same as you would have if you had table with employees stamping in and out of work and wanted to find out how much they actually were at work. I'm sure there must be well known solutions to this, but I can't seem to find them...

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  • How to research unmanaged memory leaks in .NET?

    - by Brandon
    I have a WCF service running over MSMQ. Memory gradually increases over time, indicating that there is some sort of memory leak. I ran the service locally and monitored some counters using PerfMon. Total CLR memory managed heap bytes remains relatively constant, while the process' private bytes increases over time. This leads me to believe that there is some sort of unmanaged memory leak. Assuming that unmanaged memory leak is the issue, how do I address the issue? Are there any tools I could use to give me hints as to what is causing the unmanaged memory leak? Also, all my service is doing is reading from the transactional queue and writing to a database, all as part of a DTC transaction (handled under the hood by requiring a transaction on the service contract). I am not doing anything explicitly with COM or DllImports. Thanks in advance!

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  • Foreach loop problem for Iqueyable object

    - by Vikas
    Hi, Can we use foreach loop for Iqueryable object? I'd like to do something as follow: query = Iqueryable<Myclass> = objDataContext.Myclass; // objDataContext is an object of LINQ datacontext class int[] arr1 = new int[] { 3, 4, 5 }; foreach (int i in arr1) { query = query.Where(q => (q.f_id1 == i || q.f_id2 == i || q.f_id3 == i)); } It gives me wrong output as each time value if i is changed.

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  • How to renumber primary index.

    - by Kamil Mroczek
    I have got a simple MySQL table and primary index (id) is not numbered one by one (1, 31, 35, 100 etc.). I want them to be numbered like (1, 2, 3, 4). Please tell me how to do it. I would also like to point that I am aware of possible consequences of the operation, but I just want to tidy up the table.

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  • count(*) vs count(column-name) - which is more correct?

    - by bread
    Does it make a difference if you do count(*) vs count(column-name) as in these two examples? I have a tendency to always write count(*) because it seems to fit better in my mind with the notion of it being an aggregate function, if that makes sense. But I'm not sure if it's technically best as I tend to see example code written without the * more often than not. count(*): select customerid, count(*), sum(price) from items_ordered group by customerid having count(*) > 1; vs. count(column-name): SELECT customerid, count(customerid), sum(price) FROM items_ordered GROUP BY customerid HAVING count(customerid) > 1;

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  • The best practice to setup hierarchy data

    - by eski
    I'm trying to figure out the best practice to setup hierarchy data that i take from a database into some contoller that would show the hierachy. Basicly this would look like a normal tree but when you press the items that are under "chapters" you get a link to another page. I have these tables and this is the way they are connected Period Courses Subjects Chapters I select Period from a DropDownBox and then i want all the courses in that period to line up. Under each course would be the subject and under them are the chapers, typical hierarchy. The tables are linked together with refrences to each other in linear way. I have tried to use treeview to show this, but dont understand how to do it. I though i could use <ul><il> tags and do it at runtime. Reapeter or datalist, possible ? Is it better to do this with databinding in XAML or in code ?

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  • Any way to make this PostgreSQL count query any faster?

    - by Ben Dauphinee
    I'm running a case-insensitive search on a table with 7.2 million rows, and I was wondering if there was any way to make this query any faster? Currently, it takes approx 11.6 seconds to execute, with just one search parameter, and I'm worried that as soon as I add more than one, this query will become massively slow. SELECT count(*) FROM "exif_parse" WHERE (description ~* 'canon')

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  • iPhone SDK: Data Synchronization

    - by buzzappsoftware
    I am looking for an overview of data synchronization techniques available on the iPhone platform. We need the ability to be able to sync a subset of content from a server to a local database residing on the iPhone. On other projects I have worked on, the data synchronization was handled by the database. Is that available in SQLite? If not, any suggestions on techniques? Rolling our own would not be my first choice. Thanks in advance.

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  • Wildcard in query for ASP.NET GridView

    - by cinu
    I am using GridView in ASP.NET 2.0. I am want to show the details from 3 tables (SQL2005) in the GridView per my search crieteria (Name of Visitor,Passport Number,Name of Company). It is working, but I want to use a wildcard for searching by first letter of "Name of Visitor". I have my code in the QueryBuilder in GridView (using Configure Datasource). The query is as follows: SELECT FormMaster.NameofCompany, VisitorMaster.NameofVisitor, VisitorMaster.PassportNumber, FormMaster.FormID, VisitorMaster.VisitorID FROM VisitorMaster INNER JOIN VisitorDetails ON VisitorMaster.VisitorID = VisitorDetails.VisitorID INNER JOIN FormMaster ON VisitorDetails.FormID = FormMaster.FormID WHERE (FormMaster.FormStatusID = 1) AND (VisitorMaster.PassportNumber = @PassportNumber ) OR (VisitorMaster.NameofVisitor = @NameofVisitor) OR (FormMaster.NameofCompany = @NameofCompany )

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  • Linqbuilder Query with an OrderBy

    - by Renshai
    I have a 1 : M relationship. I built a dynamic query based on input from users to return the listing of parents entities along with their children (using predicate builder: (done successfully new TDataContext().Ps.Where(predicate) )... but need to order the results by a field found only on the child entities. I'm at a loss: new TDataContext().Ps.Where(predicate).OrderBy(p = p.Cs. ??) where Ps = parents collection relationship with Cs = child entities any help appreciated.

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  • Left outer joins that don't return all the rows from T1

    - by Summer
    Left outer joins should return at least one row from the T1 table if it matches the conditions. But what if the left outer join performs a join successfully, then finds that another criterion is not satisfied? Is there a way to get the query to return a row with T1 values and T2 values set to NULL? Here's the specific query, in which I'm trying to return a list of candidates, and the user's support for those candidates IF such support exists. SELECT c.id, c.name, s.support FROM candidates c LEFT JOIN support s on s.candidate_id = c.id WHERE c.office_id = 5059 AND c.election_id = 92 AND (s.user_id = 2 OR s.user_id IS NULL) --This line seems like the problem ORDER BY c.last_name, c.name The query joins the candidates and support table, but finds that it's a different user who supported this candidate (user_id=3, say). Then the candidate disappears entirely from the result set.

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  • Using LEFT JOIN to only selection one joined row

    - by Alex
    I'm trying to LEFT JOIN two tables, to get a list of all rows from TABLE_1 and ONE related row from TABLE_2. I have tried LEFT JOIN and GROUP BY c_id, however I wan't the related row from TABLE_2 to be sorted by isHeadOffice DESC. Here are some sample tables TABLE 1 c_id Name ---------------- 1 USA 2 Canada 3 England 4 France 5 Spain TABLE2 o_id c_id Office isHeadOffice ------------------------------------------------ 1 1 New York 1 2 1 Washington 0 3 1 Boston 0 4 2 Toronto 0 5 3 London 0 6 3 Manchester 1 7 4 Paris 1 8 4 Lyon 0 So what I am trying to get from this would be something like: RESULTS c_id Name Office ---------------------------- 1 USA New York 2 Canada Toronto 3 England Manchester 4 France Paris 5 Spain NULL I'm using PHP & MySQL. Any ideas?

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  • How to filter rows on a complex filter

    - by dan
    I have these rows in a table ID Name Price Delivery == ==== ===== ======== 1 apple 1 1 2 apple 3 2 3 apple 6 3 4 apple 9 4 5 orange 4 6 6 orange 5 7 I want to have the price at the third delivery (Delivery=3) or the last price if there's no third delivery. It would give me this : ID Name Price Delivery == ==== ===== ======== 3 apple 6 3 6 orange 5 7 I don't necessary want a full solution but an idea of what to look for would be greatly appreciated.

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  • Query for multiple joins

    - by Shailaja
    i have 3 tables named dataset,dataelem and transformdataelem with column names as below: main.Dataset ------------ datasetID (PK) applicationID main.Dataelem ------------- dataelemID(PK) datasetID(FK) dataelemname biztermID main.Transformdataelem ---------------------- OutputdataelemID InputdataelemID My requirement is: All tables are referenced. Extract all the dataelemId rows from dataelem table where applicationID of dataset table is equal to 1044 and biztermid shud be null. Then whatever resultant dataelemIDs from the above query should be matched with outputdataelemID of Transformdataelem table and we shud get the respective input dataelemId's. Again with these matched inputdataelemID's we shud get the dataelemname's from datelem table.

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  • Query - Trying to SUM one field based on content of another field

    - by ShaneL
    Table: DayOfWeek Enrollments Monday 35 Monday 12 Saturday 25 Tuesday 15 Monday 9 Tuesday 15 Basically I'm trying to sum the total enrolments for each day. so the Output will look like: DayOfWeek Enrollments Monday 56 Saturday 25 Tuesday 30 I've spent around 4 hours trying to work this out trying many many different ways but no luck. The problem I'm having is i can count how many enrollments for each day but can't have it aligned with the correct day when i run the query e.g. I want The total to be on the same line as the day it was calculated from. (I hope that is clear enough)

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