Databases
StackOverflow2013
Postsdbo
POSQL Calculate (time) gap between occurrences in a log
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POSQL Calculate (time) gap between occurrences in a log
    primarykey
    data
    text
    <p>I have tables that record when certain items were sent or returned to a particular location, and I want to work out the intervals between each time a particular item is returned.</p> <p>Sample data:</p> <pre><code>Item ReturnDate: Item1, 20120101 Item1, 20120201 Item1, 20120301 Item2, 20120401 Item2, 20120601 </code></pre> <p>So in this case, we can see that the there was a month gap until Item 1 was returned the first time, and another month before it was returned the second time. Item 2 came back after 2 months.</p> <p>My starting point is:</p> <pre><code>Select r1.Item, r1.ReturnDate, r2.Item, r2.ReturnDate, DateDiff(m, r1.ReturnDate, r2.ReturnDate) from Returns r1 inner join Returns r2 on r2.VehicleNo = r1.VehicleNo </code></pre> <p>However, in the this sample, each item is compared to every other instance where it has been returned - and not just the next one. So I need to limit this query so it will only compare adjacent returns.</p> <p>One solution is to tag each return with an count (of the number of times that item has been returned):</p> <pre><code>Item ReturnDate, ReturnNo: Item1, 20120101, 1 Item1, 20120201, 2 Item1, 20120301, 3 Item2, 20120401, 1 Item2, 20120601, 2 </code></pre> <p>This would enable me to use the following T-SQL (or similar):</p> <pre><code>Select r1.Item, r1.ReturnDate, r2.Item, r2.ReturnDate, DateDiff(m, r1.ReturnDate, r2.ReturnDate) from Returns r1 inner join Returns r2 on r2.VehicleNo = r1.VehicleNo and (r1.ReturnNo + 1 = r2.ReturnNo) </code></pre> <p>My first question is whether the is a sensible/optimal approach or whether there is a better approach?</p> <p>Secondly, what is the easiest/slickest means of calculating the ReturnNo?</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USCJM
    1. USCJM
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. This table or related slice is empty.
      1. VTDownMod
    2. VO
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. USDominic P
      1. VTFavorite
    3. VO
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. This table or related slice is empty.
      1. VTUpMod
    1. COCan you tell us a little about your table structure? And do you need the return number for something else?
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. USNicole Castle
    2. CO@NicoleCastle I was trying to keep the explanation generic rather than provide live DDL with more specific and less helpful terminology. Let's just say that there is a table that records the receipt of items from outside (usually the customer) and that we want to analyse the intervals between each receipt of the same items. Item and ReturnDate are all that is relevant in this case.
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. USCJM
    3. CO@NicoleCastle ... and no, I don't need the ReturnNo for anything else - it was simply to help me compare the next return for each item.
      singulars
      1. POSQL Calculate (time) gap between occurrences in a log
      1. USCJM
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload