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[Solved] SQL Query is Kicking my Ass.

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Stoic Joker:
Greetings
   So when the boss first asked me about doing this report it sounded simple enough. But after 4 days of hammering on it I've come to the conclusion that my initial assessment may have been (dead) wrong. I'm going to try to be both detailed and succinct ... So please bear with me if this gets a bit long.

   One of our internal billing systems contains historical information (Client, serial#, date, pages printed, etc.) about printers that are under contract. Circumstances being what they are (IT Happens), occasionally there are devices that don't get their counts collected. Now usually this gets caught up at a later date ... but some times certain devices slide long enough to start raising eyebrows as to their existence and condition. Which brings "us" to the report in question.

   I'm trying to create a SQL query (for a MySQL db) that will list all the devices for client X that:
1. Does not recently/currently have a billable count (Total Pages Printed = 0).
2. Shows the date of the last billable count (or the first zero count date in a contiguous historical block between then and now).


   Sound simple enough? Hopefully it is for some one here ... 'cause I'm getting my ass kicked by this thing. The relevant table structure and usage is as follows:

Columns:
Index - auto incremented (int).
SerialNo - of the device (string).
ModelName - of the device (string).
ClientID - Internal identified of customer (string).
TimeStamp - a.k.a. billing date / all devices for a given customer/date will have an identical time stamp (timestamp).
TotalPP - Total Pages Printed this will reflect the number of pages printed by that device for that billing cycle (int).

I've got close to 9 pages of failed queries and notes on what doesn't work. Nested selects tend to make the server race and die (neat trick with dual Xeons), so I've been concentrating on various self-join variations. But nothing is giving me a resultant data set that isn't either wrong or total garbage.


So I'm hoping to find a more informed opinion on how to approach this.

Thank you,
Slightly frazzled but still vaguely Stoic Joker

justice:
(you could try <1 in case the default value for TotalPP columns empty instead of 0)

What's wrong with something like:
SELECT Max(TimeStamp) As LastBillableDate,Index,SerialNo,ModelName, ClientID FROM <TableName> WHERE TotalPP=0.

* Split the problem up into small problems you can get working, don't try it all at once.
* Microsoft Reporting Services (if you can get your hands on it) is a great tool for making reports and it can connect to MySQL databases too, this might make it easier to create reports.

Stoic Joker:
(you could try <1 in case the default value for TotalPP columns empty instead of 0)-justice (July 04, 2011, 09:30 AM)
--- End quote ---

Default column value is 0, so no NULLs to trip over/around.

What's wrong with something like:
SELECT Max(TimeStamp) As LastBillableDate,Index,SerialNo,ModelName, ClientID FROM <TableName> WHERE TotalPP=0.
-justice (July 04, 2011, 09:30 AM)
--- End quote ---

That's along the lines of what I have been playing with ... But no *joy* as of yet.

* Split the problem up into small problems you can get working, don't try it all at once.-justice (July 04, 2011, 09:30 AM)
--- End quote ---

Sound advice, but it hasn't panned out yet. :)

* Microsoft Reporting Services (if you can get your hands on it) is a great tool for making reports and it can connect to MySQL databases too, this might make it easier to create reports.-justice (July 04, 2011, 09:30 AM)
--- End quote ---

That may be handy for the future, but I'm not sure I want to introduce a new tools learning curve to the mix at this point.



Here's one of the Close-but-no-Cigar queries I've been playing with. Note it does include references to another table which is required for the final product. But isn't part of the current sticking point.

--- Code: Text ---SELECT Pc1.ClientID, Pc1.SerialNo, Pc1.ModelName, PiX.CurLocation, Pc1.TimeStamp FROM PageCounts Pc1 INNER JOIN PageCounts Pc2 ON Pc1.SerialNo = Pc2.SerialNo INNER JOIN Printer_Inv PiX ON Pc1.SerialNo = PiX.SerialNo WHERE Pc1.ClientID = 'Client X' AND PiX.Active = 1 GROUP BY Pc1.SerialNo, Pc1.TimeStamp HAVING Pc1.TimeStamp = MAX(Pc2.TimeStamp) ORDER BY Pc1.TimeStamp DESC LIMIT 0, 300

justice:
It's very hard to help you without seeing an example database, but I think the problem is between line 5-7.
If you look at the
documentation on group by / having you see Having is used as a where on groups.

I'm still not really sure what you want because the query you are posting is not the same as your description of the query in the starting post.
Your query is trying to search for a Client that is Active where the billing date from pc1 historyical information is identical to the last billing date from some other place (pc2), then grouping by printer and timestamp. It doesn't make sense.

Also to me it's not clear how Pc2 is related to pc1 :P in english? Without being clear how you want the query in english noone can translate that to SQL. hope that helps

Stoic Joker:
It's very hard to help you without seeing an example database, but I think the problem is between line 5-7.
If you look at the
documentation on group by / having you see Having is used as a where on groups.-justice (July 04, 2011, 10:25 AM)
--- End quote ---

Having is something I just ran across the other day while Googling for an example of how best to get a list of max(dates) out of a table during/using a self join. So given that it has yet to create a result set that made complete sense it's quite likely I'm using it wrong...or expecting it to do more than it actually does (hell if I knew what I was doing I'd probably be done by now... (hehe)). Also that's just one of a multitude of things I tried none of which worked properly.

Not sure how well this will paste, but here's a small (cleaned) piece of the table's content.

--- Code: Text ---Index  SerialNo         ModelName       ClientID        CurPageCount  OldPageCount      TimeStamp               TotalPP29      CNBM044207      3380 mfp        MIKLA01         2404            26              2005-10-27 09:04:17     2378 9      USLH039092      1100            CRITR01         39339           38834           2005-09-29 11:47:17     50510      CNDIF23087      1160            CRITR01         7947            7632            2005-09-29 11:47:17     31530      USBNL12704      4200            MIKLA01         199451          193626          2005-10-27 09:04:17     582512      CN09506649      4300            CRITR01         401922          383635          2005-09-29 11:47:17     1828713      JPCG012675      4v              CRITR01         449756          449206          2005-09-29 11:47:17     55014      USBB019753      8000 series     CRITR01         844310          839591          2005-09-29 11:47:17     471915      USBB020920      8000 series     CRITR01         760125          756990          2005-09-29 11:47:17     313516      U61036C5J482752 Brother MFC8840D CRITR01        3271            2314            2005-09-29 11:47:17     95718      USBB031505      3100 fax        SNIFFERT_B      167316          167316          2005-10-02 11:47:23     019      USCC000104      4050            UFORA03         258810          255488          2005-10-04 08:50:26     332220      JPJB002010      Color 8550 series ECODE01       162675          160416          2005-10-18 16:27:32     225921      USLH039092      1100            CRITR01         39945           39339           2005-10-19 08:52:25     60622      CNDIF23087      1160            CRITR01         9131            7947            2005-10-19 08:52:25     118424      CN09506649      4300            CRITR01         426537          401922          2005-10-19 08:52:25     2461525      JPCG012675      4v              CRITR01         450190          449756          2005-10-19 08:52:25     43426      USBB019753      8000 series     CRITR01         848516          844310          2005-10-19 08:52:25     420627      USBB020920      8000 series     CRITR01         768063          760125          2005-10-19 08:52:25     793828      U61036C5J482752 Brother MFC8840D CRITR01        4225            3271            2005-10-19 08:52:25     95431      USSC016017      4000 series     OCLAD01         124823          124164          2005-10-27 13:25:31     659

I'm still not really sure what you want because the query you are posting is not the same as your description of the query in the starting post.-justice (July 04, 2011, 10:25 AM)
--- End quote ---

The relevant part is. There are just some other (device specific) values being pulled in from another (PiX) table.

Your query is trying to search for a Client that is Active where the billing date from pc1 historyical information is identical to the last billing date from some other place (pc2), then grouping by printer and timestamp. It doesn't make sense.-justice (July 04, 2011, 10:25 AM)
--- End quote ---

I had a feeling that might confuse thing, which is why I didn't lead with it. Just ignore all the PiX.* stuff. It's only verifying that the device with SN X is "active" to thin out the data set.

Also to me it's not clear how Pc2 is related to pc1 :P in english? Without being clear how you want the query in english noone can translate that to SQL. hope that helps-justice (July 04, 2011, 10:25 AM)
--- End quote ---

Hm... (a bit sketchy on that myself), Best I can tell table is joined to itself on SN so that each SN can be searched for/aligned to its maximum date with a TotallPP of 0.

I'm at a point where the more I look at it the less sense it makes (forest for trees??) even after taking a break.

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