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• Help with query

  - by hdoe123

  Hi, I'm trying make a query that looks at a single table and looks to see if a student is a team called CMHT and in a medic team - if they are I don't want to see the result. I only want see if there only in CMHT or medic not both. Would the right direction be using sub query to filer it out? I've done a search on NOT IN but how could you get to see check if its in more then 2 teams are not? Student Team ref 1 CMHT 1 1 Medic 2 2 Medic 3 this would be in the result 3 CMHT 5 this would be in the result So far I've done the following code would I need use a sub query or do a self join and filter it that way? SELECT Table1.Student, Table1.Team, Table1.refnumber FROM Table1 WHERE (((Table1.Team) In ('Medics','CMHT'))

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• ORA-01722: invalid number

  - by Lluis Martinez

  I'm getting the infamous invalid number Oracle error. Hibernate is issuing an INSERT with a lot of columns, I want to know just the name of the column giving the problem. Is it possible? I hate Oracle messages, in 15 years they haven't improved a bit (the reason why is beyond my imagination). FYI the insert is this: insert into GEM_INVOICE_HEADER (ENDORSEE_ACCOUNT_ID, INVOICE_CODE, APPROVAL_ORGAN, APROVAL_DATE, APROVAL_REFERENCE, BALANCE_BASE_AMOUNT, BALANCE_DEDUCT_AMOUNT, BALANCE_TOTAL_AMOUNT, BALANCE_VAT_AMOUNT, BALANCE_VAT_DED_AMOUNT, BALANCE_VAT_NOT_DED_AMOUNT, DESCRIPTION, SUPPLIER_INVOICE_NUMBER, INVOICE_DATE, RECEIPT_DATE, MEMO, VAT_INTRACOM, INVOICE_BASE_AMOUNT, INVOICE_VAT_AMOUNT, INVOICE_VAT_DED_AMOUNT, INVOICE_VAT_NOT_DED_AMOUNT, INVOICE_DEDUCT_AMOUNT, INVOICE_TOTAL_AMOUNT, VAT_EXEMPT, RECTIFICATION_SIGN, REASON, LOT, FILE_ID, RETAINED, INSTITUTION_ID, PERIOD_CODE, IS_RECTIFIED, DEFAULT_OFFBUDGET_ACCOUNT, OFFBUDGET_DOC_ID, PHASE_OF_ACCOUNTING, ACCOUNTED_OFF_BUDGET, CANCEL_DOC_ID, BUDGET_TYPE, INVOICE_TYPE, SOURCE_ID, STATE_ID, MANAGER_UNIT_ID, DOCUMENT_TYPE_CODE, ACCOUNTED_DOC_ID, ACCOUNTING_LIST, ENDORSEE_ID, PAYMASTER_ID, SUPPLIER_ID, SUPPLIER_ACCOUNT_ID, PAY_JUSTIFY_ID, PETTY_CASH_ID, DBOID) values (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)

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• Should I commit or rollback a transaction that creates a temp table, reads, then deletes it?

  - by Triynko

  To select information related to a list of hundreds of IDs... rather than make a huge select statement, I create temp table, insert the ids into it, join it with a table to select the rows matching the IDs, then delete the temp table. So this is essentially a read operation, with no permanent changes made to any persistent database tables. I do this in a transaction, to ensure the temp table is deleted when I'm finished. My question is... what happens when I commit such a transaction vs. let it roll it back? Performance-wise... does the DB engine have to do more work to roll back the transaction vs committing it? Is there even a difference since the only modifications are done to a temp table? Related question here, but doesn't answer my specific case involving temp tables: http://stackoverflow.com/questions/309834/should-i-commit-or-rollback-a-read-transaction

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• Stored Procedure in Entity Framework

  - by kamal

  Hi I had added the Stored procedure in my Entity framework and i also imported the functions in the edmx. Is it must to add all the three functions insert, update, and delete functions to a table. I had tried with insert alone and also with all, but why can't i get the name of the stored procedure in the connection string. Let me know what i done clearly. I had added the sp i had imported the functions in the model browser. i had also mapped the insert, update and delete function to the table with return type only for insert and update. Still i can't get the name of SP in the connection string. Please let me know how could i resolve this issue. Thanks in Advance, Kamal.

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• Arguments for moving from LINQtoSQL to Nhibernate?

  - by sah302

  Backstory: Hi all, I just spent a lot of time reading many of the LINQ vs Nhibernate threads here and on other sites. I work in a small development team of 4 people and we don't even have really any super experienced developers. We work for a small company that has a lot of technical needs but not enough developers to implement them (and hiring more is out of the question right now). Typically our projects (which individually are fairly small) have been coded separately and weren't really layered in anyway, code wasn't re-used, no class libraries, and we just use the LINQtoSQL .dbml files for our pojects, we really don't even use objects but pass around values and stuff, the only time we use objects is when inserting to a database (heck not even querying since you don't need to assign it to a type and can just bind to gridview). Despite all this as I said our company has a lot of technical needs, no one could come to us for a year and we would have plenty of work to implement requested features. Well I have decided to change that a bit first by creating class libraries and actually adding layers to our applications. I am trying to meet these guys halfway by still using LINQtoSQL as the ORM yet and still use VB as the language. However I am finding it a b***h of a time dealing with so many thing in LINQtoSQL that I found easy in Nhibernate (automatic handling of the session, criteria creation easier than expression trees, generic an dynamic querying easier etc.) So... Question: How can I convince my lead developers and other senior programmers that switching to Nhibernate is a good thing? That being in control of our domain objects is a good thing? That being able to implement interfaces is a good? I've tried exlpaining the advantages of this before but it's not understood by them because they've never programmed in a true OO & layered way. Also one of the counter arguments to this I can see is sqlMetal generates those classes automatically and therefore it saves a lot of time. I can't really counter that other than saying spending more time on infrastructure to make it more scalable and flexible is good, but they can't see how. Again, I know the features and advantages (somewhat enough I believe) of each, but I need arguments applicable to my context, hence why I provided the context. I just am not a very good arguer I guess. (Caveat: For all the LINQtoSQL lovers, I may just not be super proficient as LINQ, but I find it very cumbersome that you are required to download some extra library for dynamic queries which don't by default support guid comparisons, and I also find the way of updating entitites to be cumbersome as well in terms of data context managing, so it could just be that I suck hehe.)

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• Data Modeling of Entity with Attributes

  - by StackOverflowNewbie

  I'm storing some very basic information "data sources" coming into my application. These data sources can be in the form of a document (e.g. PDF, etc.), audio (e.g. MP3, etc.) or video (e.g. AVI, etc.). Say, for example, I am only interested in the filename of the data source. Thus, I have the following table: DataSource Id (PK) Filename For each data source, I also need to store some of its attributes. Example for a PDF would be "numbe of pages." Example for audio would be "bit rate." Example for video would be "duration." Each DataSource will have different requirements for the attributes that need to be stored. So, I have modeled "data source attribute" this way: DataSourceAttribute Id (PK) DataSourceId (FK) Name Value Thus, I would have records like these: DataSource->Id = 1 DataSource->Filename = 'mydoc.pdf' DataSource->Id = 2 DataSource->Filename = 'mysong.mp3' DataSource->Id = 3 DataSource->Filename = 'myvideo.avi' DataSourceAttribute->Id = 1 DataSourceAttribute->DataSourceId = 1 DataSourceAttribute->Name = 'TotalPages' DataSourceAttribute->Value = '10' DataSourceAttribute->Id = 2 DataSourceAttribute->DataSourceId = 2 DataSourceAttribute->Name = 'BitRate' DataSourceAttribute->Value '16' DataSourceAttribute->Id = 3 DataSourceAttribute->DataSourceId = 3 DataSourceAttribute->Name = 'Duration' DataSourceAttribute->Value = '1:32' My problem is that this doesn't seem to scale. For example, say I need to query for all the PDF documents along with thier total number of pages: Filename, TotalPages 'mydoc.pdf', '10' 'myotherdoc.pdf', '23' ... The JOINs needed to produce the above result is just too costly. How should I address this problem?

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• TSQL: finding unique entries in a single table

  - by pcampbell

  Consider a table or CTE structured like this: Name Num ---- ---- Abc 12 Abc 12 XYZ 70 XYZ 80 Bar 50 Bar 55 Foo 44 Foo 44 Baz 88 The requirement is to determine the Name where multiple different Nums exist. The desired resultset is Name ---- XYZ Bar What TSQL statement would you use to derive this resultset?

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• Two different tables or just one with bool column?

  - by Aidas

  We have two tables: OriginalDocument and ProcessedDocument. In the first one we put an original, not processed document. After it's validated and processed (converted to our xml format and parsed), it's put into Document table. Processed document can be valid or invalid. Which makes more sense: have two different tables for valid and invalid documents or just have one with 'Valid' column? Some of the columns (~5-7) are irrelevant for invalid document. Storing both invalid and valid documents would also make Document table filled with 'NULL' columns (if document is invalid, information like document number, receiver can be unknown). What else should we consider and weigh, when making this decision?

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• Adding rows with linq trouble with reference table

  - by Laurence Burke

  I am adding a new address and I know the structure as AddressID = PK and all other entities are non nullable. Now on insert of a new row the addrID Pk is autogened and I am wondering if I would have to get that to create a new row in the referencing table EmployeeAddress or does that automatically get generated also. also I want to be able to repopulate the dropdownlist that lists the current employee's addresses with the newly created address. static uint _curEmpID; protected void btnAdd_Click(object sender, EventArgs e) { if (txtZip.Text != "" && txtAdd1.Text != "" && txtCity.Text != "") { TestDataClassDataContext dc = new TestDataClassDataContext(); Address addr = new Address() { AddressLine1 = txtAdd1.Text, AddressLine2 = txtAdd2.Text, City = txtCity.Text, PostalCode = txtZip.Text, StateProvinceID = Convert.ToInt32(ddlState.SelectedValue) }; dc.Addresses.InsertOnSubmit(addr); lblSuccess.Visible = true; lblErrMsg.Visible = false; dc.SubmitChanges(); // // TODO: insert new row in EmployeeAddress to reference CurEmp to newly created address // SetAddrList(); } else { lblErrMsg.Text = "Invalid Input"; lblErrMsg.Visible = true; } } protected void ddlAddList_SelectedIndexChanged(object sender, EventArgs e) { lblErrMsg.Visible = false; lblSuccess.Visible = false; TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; if (ddlAddList.SelectedValue != "-1") { var addr = (from a in dc.Addresses where a.AddressID == Convert.ToInt32(ddlAddList.SelectedValue) select a).FirstOrDefault(); txtAdd1.Text = addr.AddressLine1; txtAdd2.Text = addr.AddressLine2; txtCity.Text = addr.City; txtZip.Text = addr.PostalCode; ddlState.SelectedValue = addr.StateProvinceID.ToString(); btnSubmit.Visible = true; btnAdd.Visible = false; } else { txtAdd1.Text = ""; txtAdd2.Text = ""; txtCity.Text = ""; txtZip.Text = ""; btnAdd.Visible = true; btnSubmit.Visible = false; } } protected void SetAddrList() { TestDataClassDataContext dc = new TestDataClassDataContext(); dc.ObjectTrackingEnabled = false; var addList = from addr in dc.Addresses from eaddr in dc.EmployeeAddresses where eaddr.EmployeeID == _curEmpID && addr.AddressID == eaddr.AddressID select new { AddValue = addr.AddressID, AddText = addr.AddressID, }; ddlAddList.DataSource = addList; ddlAddList.DataValueField = "AddValue"; ddlAddList.DataTextField = "AddText"; ddlAddList.DataBind(); ddlAddList.Items.Add(new ListItem("<Add Address>", "-1")); } OK I am hoping that I did not include too much code. I would really appreciate any other comments about I could otherwise improve this code in any other ways also.

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• Loop Control within a DataflowTask in ETL

  - by Ben

  Hi, Being fairly new to SSIS and the ETL process, I was wondering if there is anyway to loop though a record set within a DataFlowTask and pass each row (deriving parameters from the row) into a Stored Procedure (the next step in the ETL phase). Once i have passed the row into the stored procedure, I want the results from each iteration to be written to a Table. Does anyone know how to do this? Thanks.

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• Why i cant save a long text on my MySQL database?

  - by DomingoSL

  im trying to save to my data base a long text (about 2500 chars) input by my users using a web form and passed to the server using php. When i look in phpmyadmin, the text gets crop. How can i config my table in order to get the complete text? This is my table config: CREATE TABLE `extra_879` ( `id` bigint(20) NOT NULL auto_increment, `id_user` bigint(20) NOT NULL, `title` varchar(300) NOT NULL, `content` varchar(3000) NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `id_user` (`id_user`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=4 ; Take a look of the field content that have a limit of 3000 chars, but the texts always gets crop at 690 chars. Thanks for any help! EDIT: I found the problem but i dont know how to solve it. The query is getting crop always in the same char, an special char: ù EDIT 2: This is the cropped query: INSERT INTO extra_879 (id,id_user,title,content) VALUES (NULL,'1','Informazione Extra',' Riconoscimenti Laurea di ingegneria presa a le 22 anni e in il terso posto della promozione Diploma analista di sistemi ottenuto il rating massimo 20/20, primo posto della promozione. Borsa di Studio (offerta dal Ministero Esteri Italiano) vinta nel 2010 (Valutazione del territorio attraverso le nueve tecnologie) Pubblicazione di paper; Stima del RCS della nave CCGS radar sulla base dei risultati di H. Leong e H. Wilson. http://www.ing.uc.edu.vek-azozayalarchivospdf/PAPER-Sarmiento.pdf Tesi di laurea: PROGETTAZIONE E REALIZZAZIONE DI UN SIS-TEMA DI TELEMETRIA GSM PER IL CONTROLLO DELLO STATO DI TRANSITO VEICOLARE E CLIMA (ottenuto il punteggio pi') It gets crop just when the (ottenuto il punteggio più alto) phrase, just when ù appear... EDIT 3: I using jquery + ajax to send the query $.ajax({type: "POST", url: "handler.php", data: "e_text="+ $('#e_text').val() + "&e_title="+ $('#extra_title').val(),

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• Jasper error: Caused by SQLServerException: Transaction (Process ID 58) was deadlocked on thread | c

  - by Saky

  I got the above error in my jasper report mail. The query that is used in the report is quite complicated (for me). Reading different posts I conclude that to solve this the I have to change the query to SET TRANSACTION ISOLATION LEVEL REPEATABLE READ GO BEGIN TRANSACTION ... my query ... COMMIT TRANSACTION ? I wonder if this is the correct way to solve the error and that if it has any side effects? Has it happened to anyone in the Jasper reports? Does anyone know if there is a better solution exist to the problem? (Although that I have not yet tested the above solution, if anyone can give any insight on this will be helpful.)

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• mysql result set joining existing table

  - by Yang

  is there any way to avoid using tmp table? I am using a query with aggregate function (sum) to generate the sum of each product: the result looks like this: product_name | sum(qty) product_1 | 100 product_2 | 200 product_5 | 300 now i want to join the above result to another table called products. so that i will have a summary like this: product_name | sum(qty) product_1 | 100 product_2 | 200 product_3 | 0 product_4 | 0 product_5 | 300 i know 1 way of doing this is the dump the 1st query result to a temp table then join it with products table. is there a better way?

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• PostgreSQL - fetch the row which has the Max value for a column

  - by Joshua Berry

  I'm dealing with a Postgres table (called "lives") that contains records with columns for time_stamp, usr_id, transaction_id, and lives_remaining. I need a query that will give me the most recent lives_remaining total for each usr_id There are multiple users (distinct usr_id's) time_stamp is not a unique identifier: sometimes user events (one by row in the table) will occur with the same time_stamp. trans_id is unique only for very small time ranges: over time it repeats remaining_lives (for a given user) can both increase and decrease over time example: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 07:00 | 1 | 1 | 1 09:00 | 4 | 2 | 2 10:00 | 2 | 3 | 3 10:00 | 1 | 2 | 4 11:00 | 4 | 1 | 5 11:00 | 3 | 1 | 6 13:00 | 3 | 3 | 1 As I will need to access other columns of the row with the latest data for each given usr_id, I need a query that gives a result like this: time_stamp|lives_remaining|usr_id|trans_id ----------------------------------------- 11:00 | 3 | 1 | 6 10:00 | 1 | 2 | 4 13:00 | 3 | 3 | 1 As mentioned, each usr_id can gain or lose lives, and sometimes these timestamped events occur so close together that they have the same timestamp! Therefore this query won't work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp) AS max_timestamp FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp = b.time_stamp Instead, I need to use both time_stamp (first) and trans_id (second) to identify the correct row. I also then need to pass that information from the subquery to the main query that will provide the data for the other columns of the appropriate rows. This is the hacked up query that I've gotten to work: SELECT b.time_stamp,b.lives_remaining,b.usr_id,b.trans_id FROM (SELECT usr_id, max(time_stamp || '*' || trans_id) AS max_timestamp_transid FROM lives GROUP BY usr_id ORDER BY usr_id) a JOIN lives b ON a.max_timestamp_transid = b.time_stamp || '*' || b.trans_id ORDER BY b.usr_id Okay, so this works, but I don't like it. It requires a query within a query, a self join, and it seems to me that it could be much simpler by grabbing the row that MAX found to have the largest timestamp and trans_id. The table "lives" has tens of millions of rows to parse, so I'd like this query to be as fast and efficient as possible. I'm new to RDBM and Postgres in particular, so I know that I need to make effective use of the proper indexes. I'm a bit lost on how to optimize. I found a similar discussion here. Can I perform some type of Postgres equivalent to an Oracle analytic function? Any advice on accessing related column information used by an aggregate function (like MAX), creating indexes, and creating better queries would be much appreciated! P.S. You can use the following to create my example case: create TABLE lives (time_stamp timestamp, lives_remaining integer, usr_id integer, trans_id integer); insert into lives values ('2000-01-01 07:00', 1, 1, 1); insert into lives values ('2000-01-01 09:00', 4, 2, 2); insert into lives values ('2000-01-01 10:00', 2, 3, 3); insert into lives values ('2000-01-01 10:00', 1, 2, 4); insert into lives values ('2000-01-01 11:00', 4, 1, 5); insert into lives values ('2000-01-01 11:00', 3, 1, 6); insert into lives values ('2000-01-01 13:00', 3, 3, 1);

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• I'm trying to handle the updates on 2 related tables in one DetailsView using Jquery and Linq, and h

  - by Ben Reisner

  Given two related tables (reports, report_fields) where there can be many report_fields entries for each reports entry, I need to allow the user to enter new report_fields, delete existing report_fields, and re-arrange the order. Currently I am using a DetailsView to handle the editing of the reports. I added some logic to handle report_fields, and currently it allows you to succesfully re-arrange the order, but i'm a little stumped as to the best way to add new items, or delete existing items. The basic logic I have is that each report_fields is represented by a . It has a description as the text, and a field for each field in the report_fields table. I use JQuery Sortable to allow the user to re-arrange the LIs. Abbreviated Create Table Statements:(foreign key constraint ignored for brevity) create table report( id integer primary key identity, reportname varchar(250) ) create table report_fields( id integer primary key identity, reportID integer, keyname integer, keyvalue integer, field_order integer ) My abbreviated markup: <asp:DetailsView ...> ... <asp:TemplateField HeaderText="Fields"> <EditItemTemplate> <ul class="MySortable"> <asp:Repeater ID="Repeater1" runat="server" DataSource='<%# Eval("report_fields") %>'> <ItemTemplate> <li> <%# Eval("keyname") %>: <%# Eval("keyvalue") %> <input type="hidden" name="keyname[]" value='<%# Eval("keyname") %>' /> <input type="hidden" name="keyvalue[]" value='<%# Eval("keyvalue") %>' /> </li> </ItemTemplate> </asp:Repeater> </ul> </EditItemTemplate> </asp:TemplateField> </asp:DetailsView> <asp:LinqDataSource ID="LinqDataSource2" onupdating="LinqDataSource2_Updating" table=reports ... /> $(function() { $(".MySortable").sortable({ placeholder: 'MySortable-highlight' }).disableSelection(); }); Code Behind Class: public partial class Administration_AddEditReport protected void LinqDataSource2_Updating(object sender, LinqDataSourceUpdateEventArgs e) { report r = (report)e.NewObject; MyDataContext dc = new MyDataContext(); var fields = from f in dc.report_fields where f.reportID == r.id select f; dc.report_fields.DeleteAllOnSubmit(fields); NameValueCollection nvc = Request.Params; string[] keyname = nvc["keyname[]"].Split(','); string[] keyvalue = nvc["keyvalue[]"].Split(','); for (int i = 0; i < keyname.Length; i++) { report_field rf = new report_field(); rf.reportID = r.id; rf.keyname = keyname[i]; rf.keyvalue = keyvalue[i]; rf.field_order = i; dc.report_fields.InsertOnSubmit(rf); } dc.SubmitChanges(); } }

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• how to get last inserted id - zend

  - by Lemon

  I'm trying to get latest inserted id from a table using this code: $id = $tbl->fetchAll (array('public=1'), 'id desc'); but it's always returning "1" any ideas? update: I've just discovered toArray();, which retrieves all the data from fetchAll. The problem is, I only need the ID. My current code looks like this: $rowsetArray = $id->toArray(); $rowCount = 1; foreach ($rowsetArray as $rowArray) { foreach ($rowArray as $column => $value) { if ($column="id") {$myid[$brr] = $value;} //echo"\n$myid[$brr]"; } ++$rowCount; ++$brr; } Obviously, I've got the if ($column="id") {$myid[$brr] = $value;} thing wrong. Can anyone point me in the right direction? An aternative would be to filter ID's from fetchAll. Is that possible?

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• DataContext Refresh and PropertyChanging & PropertyChanged Events

  - by Scott

  I'm in a situation where I am being informed from an outside source that a particular entity has been altered outside my current datacontext. I'm able to find the entity and call refresh like so MyDataContext.Refresh(RefreshMode.OverwriteCurrentValues, myEntity); and the properties which have been altered on the entity are updated correctly. However neither of the INotifyPropertyChanging INotifyPropertyChanged appear to be raised when the refresh occurs and this leaves my UI displaying incorrect information. I'm aware that Refresh() fails to use the correct property getters and setters on the entity to raise the change notification events, but perhaps there is another way to accomplish the same thing? Am I doing something wrong? Is there a better method than Refresh? If Refresh is the only option, does anyone have a work around?

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• Struggling to create correct relationships in MS Access

  - by Yandawl

  http://img714.imageshack.us/img714/7820/croppercapture1.png Basically: an award(course) has many units, which can be either optional or core(mandatory), depending on the award. So for example: the unit 'Advanced Software Engineering' maybe a core unit for the award 'Software Engineering BSc' but only an optional unit for the course 'Web Technology BSc'. I've used flags for that purpose. A student is enrolled on an award so I need to get a complete list of core and optional units (bearing in mind that a student chooses 1 out of many possible optional units). Also, these units have events, e.g, a lecture, workshop or seminar, etc. and those events have sessions or instances of events where students enrolled on that particular unit are required to attend, and those attendances are stored in a separate table to form a register. So I need a hierarchy of expanding the tables something like this I guess: Awards - Students - Units - Sessions - Attendances Any help with this would be appreciated... It's blowing my mind and I'm really close to going insane! My tutor didn't spot I'd got it wrong when I showed my original data model to him and it's due in next week! Thank you :D

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• how to connect sqlserver cubes using dotnet(C#)

  - by prince23

  hi. i am new to this cubes concept in sqlserver . i need to connect to cubes and and query and get an result and display that result in grid view any help would be great telling how to connect to an cube, articles on it, code any thing that can help me to achieve the result thank you.

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• Spaced repetition (SRS) for learning

  - by Fredrik Johansson

  A client has asked me to add a simple spaced repeition algorithm (SRS) for an onlinebased learning site. But before throwing my self into it, I'd like to discuss it with the community. Basically the site asks the user a bunch of questions (by automatically selecting say 10 out of 100 total questions from a database), and the user gives either a correct or incorrect answer. The users result are then stored in a database, for instance: userid questionid correctlyanswered dateanswered 1 123 0 (no) 2010-01-01 10:00 1 124 1 (yes) 2010-01-01 11:00 1 125 1 (yes) 2010-01-01 12:00 Now, to maximize a users ability to learn all answers, I should be able to apply an SRS algorithm so that a user, next time he takes the quiz, receives questions incorrectly answered more often; than questions answered correctly. Also, questions that are previously answered incorrectly, but recently often answered correctly should occur less often. Have anyone implemented something like this before? Any tips or suggestions? Theese are the best links I've found: http://en.wikipedia.org/wiki/Spaced_repetition http://www.mnemosyne-proj.org/principles.php http://www.supermemo.com/english/ol/sm2.htm

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• Building a subquery with ARel in Rails3

  - by Christopher

  I am trying to build this query in ARel: SELECT FLOOR(AVG(num)) FROM ( SELECT COUNT(attendees.id) AS num, meetings.club_id FROM `meetings` INNER JOIN `attendees` ON `attendees`.`meeting_id` = `meetings`.`id` WHERE (`meetings`.club_id = 1) GROUP BY meetings.id) tmp GROUP BY tmp.club_id It returns the average number of attendees per meeting, per club. (a club has many meetings and a meeting has many attendees) So far I have (declared in class Club < ActiveRecord::Base): num_attendees = meetings.select("COUNT(attendees.id) AS num").joins(:attendees).group('meetings.id') Arel::Table.new('tmp', self.class.arel_engine).from(num_attendees).project('FLOOR(AVG(num))').group('tmp.club_id').to_sql but, I am getting the error: undefined method `visit_ActiveRecord_Relation' for #<Arel::Visitors::MySQL:0x9b42180> The documentation for generating non trivial ARel queries is a bit hard to come by. I have been using http://rdoc.info/github/rails/arel/master/frames Am I approaching this incorrectly? Or am I a few methods away from a solution?

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• Displaying a single rank in MySQL table

  - by MichaelInno

  I have a table called 'highscores' that looks like this. id udid name score 1 1111 Mike 200 2 3333 Joe 300 3 4444 Billy 50 4 0000 Loser 10 5 DDDD Face 400 Given a specific udid, I want to return the rank of that row by their score value. i.e. if udid given = 0000, I should return 5. Any idea how to write this query for a MySQL database?

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• Join one row to multiple rows in another table

  - by Ghostrider

  I have a table to entities (lets call them people) and properties (one person can have an arbitrary number of properties). Ex: People Name Age -------- Jane 27 Joe 36 Jim 16 Properties Name Property ----------------- Jane Smart Jane Funny Jane Good-looking Joe Smart Joe Workaholic Jim Funny Jim Young I would like to write an efficient select that would select people based on age and return all or some of their properties. Ex: People older than 26 Name Properties Jane Smart, Funny, Good-looking Joe Smart, Workaholic It's also acceptable to return one of the properties and total property count. The query should be efficient: there are millions of rows in people table, hundreds of thousands of rows in properties table (so most people have no properties). There are hundreds of rows selected at a time. Is there any way to do it?

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• same table, 1 field to 2 field query

  - by edib

  I have 2 tables: 1st holds employees (of ones in any position) and the 2nd holds manager employee relations with id numbers. I want to write a query like 1st field: name(employee), 2nd field: name(manager) How can I do that?

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• Porting join from Oracle to Postgres

  - by Grasper

  INSERT INTO MISSION_OBJECTIVE( MSN_INT_ID, MO_INT_ID, MO_MSN_CLASS_NM, MO_MSN_CLASS_CD, MO_MSN_TYPE, MO_PRIORITY, MO_COMMENT, MO_START_DT, MO_END_DT, ASP_AIRSPACE_NM, MO_OBJ_LOCATION, MO_ALO_LEG_ID, MO_ALO_ARRIVE_LOC) SELECT '1025', '1', 'AIRDROP', 'ADP', 'LAPES', NULL, COALESCE( NULL, ' '), TO_TIMESTAMP( '1002260900', 'YYMMDDHH24MI'), TO_TIMESTAMP( '1002260915', 'YYMMDDHH24MI'), 'TRANSIT ALPHA', 'TRANSIT ALPHA', '1', 'TRANSIT ALPHA' FROM AIRSPACE ASP, apsmain .MISSION_CLASS MC WHERE ASP.ASP_AIRSPACE_NM(+)= 'TRANSIT ALPHA' AND MC.MCS_MISSION_CLASS_NAME= 'AIRDROP' AND 'TRANSIT ALPHA' IS NOT NULL Is that exactly the same as: INSERT INTO MISSION_OBJECTIVE( MSN_INT_ID, MO_INT_ID, MO_MSN_CLASS_NM, MO_MSN_CLASS_CD, MO_MSN_TYPE, MO_PRIORITY, MO_COMMENT, MO_START_DT, MO_END_DT, ASP_AIRSPACE_NM, MO_OBJ_LOCATION, MO_ALO_LEG_ID, MO_ALO_ARRIVE_LOC) SELECT '1025', '1', 'AIRDROP', 'ADP', 'LAPES', NULL, COALESCE( NULL, ' '), TO_TIMESTAMP( '1002260900', 'YYMMDDHH24MI'), TO_TIMESTAMP( '1002260915', 'YYMMDDHH24MI'), 'TRANSIT ALPHA', 'TRANSIT ALPHA', '1', 'TRANSIT ALPHA' FROM AIRSPACE ASP, apsmain .MISSION_CLASS MC WHERE ASP.ASP_AIRSPACE_NM = 'TRANSIT ALPHA' AND MC.MCS_MISSION_CLASS_NAME= 'AIRDROP' AND 'TRANSIT ALPHA' IS NOT NULL I just deleted the (+). The part that is confusing me is that ASP.ASP_AIRSPACE_NM is being right joined to a constant.

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