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  • How to avoid timestamp issue in a long query?

    - by pingi
    Hi, I have the following 2 tables: items: id int primary key bla text events: id_items int num int when timestamp without time zone ble text composite primary key: id_items, num and want to select to each item the most recent event (the newest 'when'). I wrote an request, but I don't know if it could be written more efficiently. Also on PostgreSQL there is a issue with comparing Timestamp objects: 2010-05-08T10:00:00.123 == 2010-05-08T10:00:00.321 so I select with 'MAX(num)' Any thoughts how to make it better? Thanks. SELECT i.*, ea.* FROM items AS i JOIN ( SELECT t.s AS t_s, t.c AS t_c, max(e.num) AS o FROM events AS e JOIN ( SELECT DISTINCT id_item AS s, MAX(when) AS c FROM events GROUP BY s ORDER BY c ) AS t ON t.s = e.id_item AND e.when = t.c GROUP BY t.s, t.c ) AS tt ON tt.t_s = i.id JOIN events AS ea ON ea.id_item = tt.t_s AND ea.cas = tt.t_c AND ea.num = tt.o;

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  • How to manage multiple versions of the same record

    - by Darvis Lombardo
    I am doing short-term contract work for a company that is trying to implement a check-in/check-out type of workflow for their database records. Here's how it should work... 1) A user creates a new entity within the application. There are about 20 related tables that will be populated in addition to the main entity table. 2) Once the entity is created the user will mark it as the master. 3) Another user can make changes to the master only by "checking out" the entity. Multiple users can checkout the entity at the same time. 4) Once the user has made all the necessary changes to the entity, they put it in a "needs approval" status. 5) After an authorized user reviews the entity, they can promote it to master which will put the original record in a tombstoned status. The way they are currently accomplishing the "check out" is by duplicating the entity records in all the tables. The primary keys include EntityID + EntityDate, so they duplicate the entity records in all related tables with the same EntityID and an updated EntityDate and give it a status of "checked out". When the record is put into the next state (needs approval), the duplication occurs again. Eventually it will be promoted to master at which time the final record is marked as master and the original master is marked as dead. This design seems hideous to me, but I understand why they've done it. When someone looks up an entity from within the application, they need to see all current versions of that entity. This was a very straightforward way for making that happen. But the fact that they are representing the same entity multiple times within the same table(s) doesn't sit well with me, nor does the fact that they are duplicating EVERY piece of data rather than only storing deltas. I would be interested in hearing your reaction to the design, whether positive or negative. I would also be grateful for any resoures you can point me to that might be useful for seeing how someone else has implemented such a mechanism. Thanks! Darvis

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  • Active Record/ORM vs Normal Forms?

    - by Arsenal
    Hello, I've been playing around with Active Record a bit, and I have noticed that A.C./ORM always uses the following database model when creating a one-to-one relationship Person id | country_id | name | ... Country id | tld | name | ... No I wondered, isn't this a violiation of the third Normal Form? This clearly states "Every non-prime attribute is non-transitively dependent on every key of the table". Well this country_id isn't dependent of personid is it? So is this wrong or am I just not getting the point?

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  • rails: date type and GetDate

    - by cbrulak
    This is a follow up to this question: http://stackoverflow.com/questions/2930256/unique-responses-rails-gem I'm going to create an index based on the user id, url and a date type. I want date type (not datetime type) because I want the day, the 24 hour day to be part of the index to avoid duplication of page views counts on the same day. In other words: A view only counts once in a day by a visitor. I also want the default value of that column (viewdate) to be the function GETDATE(). This is what I have in my migration: execute "ALTER TABLEpage_viewsADD COLUMN viewdate datetime DEFAULTGETDATE()`" But the value viewdate is always empty. What am I missing? (as an aside, any other suggestions for accomplishing this goal?)

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  • Precision of Interval for PL/SQL Function value

    - by Gary
    Generally, when you specify a function the scale/precision/size of the return datatype is undefined. For example, you say FUNCTION show_price RETURN NUMBER or FUNCTION show_name RETURN VARCHAR2. You are not allowed to have FUNCTION show_price RETURN NUMBER(10,2) or FUNCTION show_name RETURN VARCHAR2(20), and the function return value is unrestricted. This is documented functionality. Now, I get an precision error (ORA-01873) if I push 9999 hours (about 400 days) into the following. The limit is because the default days precision is 2 DECLARE v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return INTERVAL DAY TO SECOND IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / and it won't allow the precision to be specified directly as part of the datatype returned by the function. DECLARE v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return INTERVAL DAY (4) TO SECOND IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / I can use a SUBTYPE DECLARE subtype t_int is INTERVAL DAY (4) TO SECOND(0); v_int INTERVAL DAY (4) TO SECOND(0); FUNCTION hhmm_to_interval return t_int IS v_hhmm INTERVAL DAY (4) TO SECOND(0); BEGIN v_hhmm := to_dsinterval('PT9999H'); RETURN v_hhmm; -- END hhmm_to_interval; BEGIN v_int := hhmm_to_interval; end; / Any drawbacks to the subtype approach ? Any alternatives (eg some place to change a default precision) ? Working with 10gR2.

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  • Index on column with only 2 distinct values

    - by Will
    I am wondering about the performance of this index: I have an "Invalid" varchar(1) column that has 2 values: NULL or 'Y' I have an index on (invalid), as well as (invalid, last_validated) Last_validated is a datetime (this is used for a unrelated SELECT query) I am flagging a small amount of items (1-5%) of rows in the table with this as 'to be deleted'. This is so when i DELETE FROM items WHERE invalid='Y' it does not perform a full table scan for the invalid items. A problem seems to be, the actual DELETE is quite slow now, possibly because all the indexes are being removed as they are deleted. Would a bitmap index provide better performance for this? or perhaps no index at all?

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  • Problem with LINQ in C#

    - by David Bonnici
    I am encountering a problem when using LINQ in C#, I am constantly getting "Specified cast is not valid". This is what I am trying to do. I create a class in which I declare all the columns of the table. [Table(Name="tbl_Aff")] public class Affiliate { [Column] public string name; [Column] public string firstname; [Column] public string surname; [Column] public string title; } I then declare a strongly typed DataContext in which I declare all Table collections as members of the context. public partial class Database : DataContext { public Table affiliate; public Database() : base(Settings.getConnectionString()) { } //This method gets the connection string by reading from an XML file. } public partial class Default : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Database database = new Database(); try { var q = from a in database.affiliate select a; foreach (var aff in q) // Here I get the error "Specified cast is not valid" { lblMessage.InnerHtml += aff.name + ""; } } catch (Exception ex) { System.Console.WriteLine(ex.Message); } } }

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  • MySQL database query returns empty result

    - by user1791096
    I am doing a data migration and getting empty result of simple query with one join. Following is the query Select * from users u INNER JOIN temp_users tu ON tu.uid = u.uid There hundreds of records which have same uid in both tables, but this query returns only one record. Following is the structure of tables users table uid: varchar(50) utf8_general_ci Yes NULL temp_users table uid: varchar(50) utf8_general_ci Yes NULL Is there anyone who faced same problem?

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  • Linq is returning too many results when joined

    - by KallDrexx
    In my schema I have two database tables. relationships and relationship_memberships. I am attempting to retrieve all the entries from the relationship table that have a specific member in it, thus having to join it with the relationship_memberships table. I have the following method in my business object: public IList<DBMappings.relationships> GetRelationshipsByObjectId(int objId) { var results = from r in _context.Repository<DBMappings.relationships>() join m in _context.Repository<DBMappings.relationship_memberships>() on r.rel_id equals m.rel_id where m.obj_id == objId select r; return results.ToList<DBMappings.relationships>(); } _Context is my generic repository using code based on the code outlined here. The problem is I have 3 records in the relationships table, and 3 records in the memberships table, each membership tied to a different relationship. 2 membership records have an obj_id value of 2 and the other is 3. I am trying to retrieve a list of all relationships related to object #2. When this linq runs, _context.Repository<DBMappings.relationships>() returns the correct 3 records and _context.Repository<DBMappings.relationship_memberships>() returns 3 records. However, when the results.ToList() executes, the resulting list has 2 issues: 1) The resulting list contains 6 records, all of type DBMappings.relationships(). Upon further inspection there are 2 for each real relationship record, both are an exact copy of each other. 2) All relationships are returned, even if m.obj_id == 3, even though objId variable is correctly passed in as 2. Can anyone see what's going on because I've spent 2 days looking at this code and I am unable to understand what is wrong. I have joins in other linq queries that seem to be working great, and my unit tests show that they are still working, so I must be doing something wrong with this. It seems like I need an extra pair of eyes on this one :)

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  • Tentative date casting in tsql

    - by Tewr
    I am looking for something like TRYCAST in TSQL or an equivalent method / hack. In my case I am extracting some date data from an xml column. The following query throws "Arithmetic overflow error converting expression to data type datetime." if the piece of data found in the xml cannot be converted to datetime (in this specific case, the date is "0001-01-01" in some cases). Is there a way to detect this exception before it occurs? select [CustomerInfo].value('(//*:InceptionDate/text())[1]', 'datetime') FROM Customers An example of what I am trying to achieve in pseudocode with an imagined tsql function TRYCAST(expr, totype, defaultvalue): select TRYCAST( [CustomerInfo].value('(//*:InceptionDate/text())[1]', 'nvarchar(100)'), datetime, null) FROM Customers

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  • ora-00939 error in reporting services, SSRS

    - by san
    Hi, I have an SSRS report , Oracle is my backend and am using this following query for dataset of my second parameter. select distinct X from v_stf_sec_user_staffing_center usc where usc.center_group_id in ( select distinct center_group_id from V_T_STAFFING_CENTER_GROUP scg where INSTR(','||REPLACE(:PI_REGION_LIST,' ')||',', ','||scg.group_abbreviation||',') 0) and usc.nt_user_name=:PI_NT_USER_NAME Here PI_REGION_LIST is a multivalued parameter of string type. and PI_NT_USER_NAME is a default string valued parameter this query works fine when i try to execute in manulally in the Data tab , also in the Oracle tool. But when i run the report in SSRS and select more than 3 values for the parameter PI_REGION_LIST the report throws an error on this dataset, ora-00939 error,too many arguments for function. I am not able to figure out the error here. Please help me with an idea. Thanks in advance, Suni.

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  • Database indexes - what should they be

    - by WebweaverD
    Most of my database tables have a clear unique index through which lookups are done 90% of the time but I am a bit unsure on this one - I have a table which keeps track of user rating totals for items in my database, I now want to add another table, to track individual ratings with an ip address column to make sure no one can rate something twice. Since I can see this becoming a big, high use table it is important to optimize it correctly. (MYSQL table) This table will have the following fields: rating_id(always - unique), item_id (always - not unique), user_id (optional - not unique), ip_address (always - not unique), rating_value(always - not unique), has_review(bool) Now I envisions 90% the queries going something like this: When a user rates something - select where item_id = x and ip_address = y, (if rows = 0) insert rating When in user account pages - select where ip_address = x or username = y Now none of the fields searched on are unique, can I still use them as indexes (for example item _id and ip_address), can I have two indexes and will this still improve performance over a non indexed table?

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  • Properly populating tables in an Object Relational database

    - by chaosTechnician
    I've got a homework assignment that requires that I use Oracle 10g Express to implement an Object Relational database to track phone billing data. I have a superclass of Communications with subclasses of Call, Text, and Data. I'm hitting a snag with properly populating these tables so that I can find the appropriate data in the various tables. My Types and Tables are declared as such: create type CommunicationType as object ( -- column names here ) not final; create type CallType under CommunicationType ( -- column names here ); create type TextType under CommunicationType ( -- column names here ); create type DataType under CommunicationType ( -- column names here ); create table Communications of CommunicationType ( -- Primary and Foreign key constraints here ); create table Calls of CallType; create table Texts of TextType; create table Datas of DataType; When I try to insert data into one of the subclasses, its entry doesn't appear in the superclass. Likewise if I insert into the superclass, it doesn't show up in the appropriate subclass. For example, insert into Calls values (CallType( -- Values -- )); doesn't show any data in Communications. Nor does insert into Communications values (CallType( -- Values -- )); show anything in Calls. What am I doing wrong?

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  • ASP.NET MVC Deployed Application Server Address

    - by Jacob Huggart
    I have an application that sends an email to a user so that they may access a web form. In the email there is just a link to the start page of this form. Currently, I have the value for the form location hardcoded. Once the app is deployed I know it is in inetpub/wwwroot/appName, which results in a URL of serverip:appPort/appName. What is the C# to get the serverip:appPort portion of the URL that I need? I think that server.mappath() might work, but for some reason I can't get to the method even though I have the necessary references.

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  • SqlServer2008 + expensive union

    - by Tim Mahy
    Hi al, we have 5 tables over which we should query with user search input throughout a stored procedure. We do a union of the similar data inside a view. Because of this the view can not be materialized. We are not able to change these 5 tables drastically (like creating a 6th table that contains the similar data of the 5 tables and reference that new one from the 5 tables). The query is rather expensive / slow what are our other options? It's allowed to think outside the box. Unfortunately I cannot give more information like the table/view/SP definition because of customer confidentiality... greetings, Tim

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  • What is the best way to return result from business layer to presentation layer when using linq - I

    - by samsur
    I have a business layer that has DTOs that are used in the presentation layer. This application uses entity framework. Here is an example of a class called RoleDTO public class RoleDTO { public Guid RoleId { get; set; } public string RoleName { get; set; } public string RoleDescription { get; set; } public int? OrganizationId { get; set; } } In the BLL I want to have a method that returns a list of DTO.. I would like to know which is the better approach: returning IQueryable or list of DTOs. Although i feel that returning Iqueryable is not a good idea because the connection needs to be open. Here are the 2 different methods using the different approaches public class RoleBLL { private servicedeskEntities sde; public RoleBLL() { sde = new servicedeskEntities(); } public IQueryable<RoleDTO> GetAllRoles() { IQueryable<RoleDTO> role = from r in sde.Roles select new RoleDTO() { RoleId = r.RoleID, RoleName = r.RoleName, RoleDescription = r.RoleDescription, OrganizationId = r.OrganizationId }; return role; } Note: in the above method the datacontext is a private attribute and set in the constructor, so that the connection stays opened. Second approach public static List GetAllRoles() { List roleDTO = new List(); using (servicedeskEntities sde = new servicedeskEntities()) { var roles = from pri in sde.Roles select new { pri.RoleID, pri.RoleName, pri.RoleDescription }; //Add the role entites to the DTO list and return. This is necessary as anonymous types can be returned acrosss methods foreach (var item in roles) { RoleDTO roleItem = new RoleDTO(); roleItem.RoleId = item.RoleID; roleItem.RoleDescription = item.RoleDescription; roleItem.RoleName = item.RoleName; roleDTO.Add(roleItem); } return roleDTO; } Please let me know, if there is a better approach - Thanks,

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  • linq join query

    - by SamB09
    Hi, im trying to do a join in linq , however for some reason i cant access the primary key of a table. It's the 'h.ProjectId' that doesn't seem to be accepted. The following error is given CW1.SearchWebService.Bid does not contain a definition for 'ProjectId' and no extention method 'ProjectId' accepting a first argument of type 'CW1SearchWebService.Bid' var allProjects = ctxt.Project.ToList() ; var allBids = ctxt.Bid.ToArray();// return all bids var projects = (from project in allProjects join h in allBids on project.ProjectId equals h.ProjectId

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  • sqlite3 date and interval functions

    - by umuthorax
    Hi, I wonder whether sqlite3 supports interval function. The following statement is accepted by PostgreSQL, however sqlite3 failed to parse it; select ... from orders where ... and o_orderdate < date '1995-03-01' + interval '3' month Error: near line 4: near "'1995-03-01'": syntax error Then, I modified the statement a little bit such as; and o_orderdate < date('1995-03-01') + interval '3' month This time the error was; Error: near line 4: near "'3'": syntax error Unfortunately, same trick did not work for the interval function i.e. and o_orderdate < date('1995-03-01') + interval('3' month) or and o_orderdate < date('1995-03-01') + interval('3') month or even and o_orderdate < date('1995-03-01') + interval(3 month) still gave me the syntax error. Maybe sqlite3 does not support interval function or am I missing something in its usage? Thanks a lot

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  • Django: Determining if a user has voted or not

    - by TheLizardKing
    I have a long list of links that I spit out using the below code, total votes, submitted by, the usual stuff but I am not 100% on how to determine if the currently logged in user has voted on a link or not. I know how to do this from within my view but do I need to alter my below view code or can I make use of the way templates work to determine it? I have read http://stackoverflow.com/questions/1528583/django-vote-up-down-method but I don't quite understand what's going on ( and don't need any ofjavascriptery). Models (snippet): class Link(models.Model): category = models.ForeignKey(Category, blank=False, default=1) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) modified = models.DateTimeField(auto_now=True) url = models.URLField(max_length=1024, unique=True, verify_exists=True) name = models.CharField(max_length=512) def __unicode__(self): return u'%s (%s)' % (self.name, self.url) class Vote(models.Model): link = models.ForeignKey(Link) user = models.ForeignKey(User) created = models.DateTimeField(auto_now_add=True) def __unicode__(self): return u'%s vote for %s' % (self.user, self.link) Views (snippet): links = Link.objects.select_related().annotate(votes=Count('vote')).order_by('-created')

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  • Unit testing a SQL code generator

    - by Tom H.
    The team I'm on is currently writing code in TSQL to generate TSQL code that will be saved as scripts and later run. We're having a little difficulty in separating our unit tests between testing the code generator parts and testing the actual code that they generate. I've read through another similar question, but I was hoping to get some specific examples of what kind of unit test cases we might have. As an example, let's say that I have a bit of code that simply generates a DROP statement for a view, given the view schema and name. Do I just test that the generated code matches some expected outcome using string comparisons and then in a later integration or system test make sure that the drop actually drops the view if it exists, does nothing if the view doesn't exist, or raises an error if the view is one that we are marking as not allowing a drop? Thanks for any advice!

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  • Oracle database connection string PLSQL compatibility

    - by user521180
    Hi I'm using an application called Logi info. it requires a connection string to my oracle database. the connection works fine but in order to configure the connection to recive ref cursors from the database, I apparently need to add PLSQLRSet=1 to the end of the string. when I do that I recieve an error "invalid connection string" Here is my connection string without plsqlrset=1 Data Source=SID; User Id=username; Password=password; My concern is that PLSQLRSet=1 might be .NET paramater only. Can anyone shed some light on the issue. Thanks

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  • How to use a getter with a nullable?

    - by Desmond Lost
    I am reading a bunch of queries from a database. I had an issue with the queries not closing, so I added a CommandTimeout. Now, the individual queries read from the config file each time they are run. How would I make the code cache the int from the config file only once using a static nullable and getter. I was thinking of doing something along the lines of: static int? var; get{ var = null; if (var.HasValue) ...(i dont know how to complete the rest) My actual code: private object ExecuteQuery(string dbConnStr, bool fixIt) { object result = false; using (SqlConnection connection = new SqlConnection(dbConnStr)) { connection.Open(); using (SqlCommand sqlCmd = new SqlCommand()) { AddSQLParms(sqlCmd); sqlCmd.CommandTimeout = 30; sqlCmd.CommandText = _cmdText; sqlCmd.Connection = connection; sqlCmd.CommandType = System.Data.CommandType.Text; sqlCmd.ExecuteNonQuery(); } connection.Close(); } return result; }}

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