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  • Trigger to update data in another DB

    - by Permana
    I have the following schema: Database: test. Table: per_login_user, Field: username (PK), password Database: wavinet. Table: login_user, Field: username (PK), password What I want to do is to create a trigger. Whenever a password field on table per_login_user in database test get updated, the same value will be copied to field password in Table login_wavinet in database wavinet I have search trough Google and find this solution: http://forums.devshed.com/ms-sql-development-95/use-trigger-to-update-data-in-another-db-149985.html But, when I run this query: CREATE TRIGGER trgPasswordUpdater ON dbo.per_login_user FOR UPDATE AS UPDATE wavinet.dbo.login_user SET password = I.password FROM inserted I INNER JOIN deleted D ON I.username = D.username WHERE wavinet.dbo.login_wavinet.password = D.password the query return error message: Msg 107, Level 16, State 3, Procedure trgPasswordUpdater, Line 4 The column prefix 'wavinet.dbo.login_wavinet' does not match with a table name or alias name used in the query.

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  • How can I copy a queryset to a new model in django admin?

    - by user3806832
    I'm trying to write an action that allows the user to select the queryset and copy it to a new table. So: John, Mark, James, Tyler and Joe are in a table 1( called round 1) The user selects the action that say to "move to next round" and those same instances that were chosen are now also in the table for "round 2". I started trying with an action but don't really know where to go from here: def Round_2(modeladmin, request, queryset): For X in queryset: X.pk = None perform.short_description = "Move to Round 2" How can I copy them to the next table with all of their information (pk doesn't have to be the same)? Thanks

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  • How to add condition on multiple-join table

    - by Jean-Philippe
    Hi, I have those two tables: client: id (int) #PK name (varchar) client_category: id (int) #PK client_id (int) category (int) Let's say I have those datas: client: {(1, "JP"), (2, "Simon")} client_category: {(1, 1, 1), (2, 1, 2), (3, 1, 3), (4,2,2)} tl;dr client #1 has category 1, 2, 3 and client #2 has only category 2 I am trying to build a query that would allow me to search multiple categories. For example, I would like to search every clients that has at least category 1 and 2 (would return client #1). How can I achieve that? Thanks!

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  • Is a many-to-many relationship with extra fields the right tool for my job?

    - by whichhand
    Previously had a go at asking a more specific version of this question, but had trouble articulating what my question was. On reflection that made me doubt if my chosen solution was correct for the problem, so this time I will explain the problem and ask if a) I am on the right track and b) if there is a way around my current brick wall. I am currently building a web interface to enable an existing database to be interrogated by (a small number of) users. Sticking with the analogy from the docs, I have models that look something like this: class Musician(models.Model): first_name = models.CharField(max_length=50) last_name = models.CharField(max_length=50) dob = models.DateField() class Album(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) class Instrument(models.Model): artist = models.ForeignKey(Musician) name = models.CharField(max_length=100) Where I have one central table (Musician) and several tables of associated data that are related by either ForeignKey or OneToOneFields. Users interact with the database by creating filtering criteria to select a subset of Musicians based on data the data on the main or related tables. Likewise, the users can then select what piece of data is used to rank results that are presented to them. The results are then viewed initially as a 2 dimensional table with a single row per Musician with selected data fields (or aggregates) in each column. To give you some idea of scale, the database has ~5,000 Musicians with around 20 fields of related data. Up to here is fine and I have a working implementation. However, it is important that I have the ability for a given user to upload there own annotation data sets (more than one) and then filter and order on these in the same way they can with the existing data. The way I had tried to do this was to add the models: class UserDataSets(models.Model): user = models.ForeignKey(User) name = models.CharField(max_length=100) description = models.CharField(max_length=64) results = models.ManyToManyField(Musician, through='UserData') class UserData(models.Model): artist = models.ForeignKey(Musician) dataset = models.ForeignKey(UserDataSets) score = models.IntegerField() class Meta: unique_together = (("artist", "dataset"),) I have a simple upload mechanism enabling users to upload a data set file that consists of 1 to 1 relationship between a Musician and their "score". Within a given user dataset each artist will be unique, but different datasets are independent from each other and will often contain entries for the same musician. This worked fine for displaying the data, starting from a given artist I can do something like this: artist = Musician.objects.get(pk=1) dataset = UserDataSets.objects.get(pk=5) print artist.userdata_set.get(dataset=dataset.pk) However, this approach fell over when I came to implement the filtering and ordering of query set of musicians based on the data contained in a single user data set. For example, I could easily order the query set based on all of the data in the UserData table like this: artists = Musician.objects.all().order_by(userdata__score) But that does not help me order by the results of a given single user dataset. Likewise I need to be able to filter the query set based on the "scores" from different user data sets (eg find all musicians with a score 5 in dataset1 and < 2 in dataset2). Is there a way of doing this, or am I going about the whole thing wrong?

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  • Query multiple currencies

    - by TiuTalk
    I need store multiple currencies on my database... Here's the problem: Example Tables: [ Products ] id (INT, PK) name (VARCHAR) price (DECIMAL) currency (INT, FK) [ Currencies ] id (INT, PK) name (VARCHAR) conversion (DECIMAL) # To U$ I'll store the product price with the currency selected by the user... Later I need to search the products using a price interval like "Search products with price from U$ 50 to U$ 100" and I need the system convert these values "on the fly" to run the SQL Query and filter the products. And I really don't know how to make this query... :/

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  • SQL Syntax for Complex Scenario (Deals)

    - by Yisman
    hello everyone i have a complex query to be written but cannot figure it out here are my tables Sales --one row for each sale made in the system SaleProducts --one row for each line in the invoice (similar to OrderDetails in NW) Deals --a list of possible deals/offers that a sale may be entitled to DealProducts --a list of quantities of products that must be purchased in order to get a deal now im trying to make a query which will tell me for each sale which deals he may get the relevant fields are: Sales: SaleID (PK) SaleProducts: SaleID (FK), ProductID (FK) Deals: DealID (PK) DealProducts: DealID(FK), ProductID(FK), Mandatories (int) for required qty i believe that i should be able to use some sort of cross join or outer join, but it aint working here is one sample (of about 30 things i tried) SELECT DealProducts.DealID, DealProducts.ProductID, DealProducts.Mandatories, viwSaleProductCount.SaleID, viwSaleProductCount.ProductCount FROM DealProducts LEFT OUTER JOIN viwSaleProductCount ON DealProducts.ProductID = viwSaleProductCount.ProductID GROUP BY DealProducts.DealID, DealProducts.ProductID, DealProducts.Mandatories, viwSaleProductCount.SaleID, viwSaleProductCount.ProductCount the problem is that it doesnt show any product deals that r not fullfiled (probably because of the productid join). i need that also sales that dont have the requiremnets show up, then i can filter out any saleid that exists in this query "where AmountBought thank you for your help

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  • Please suggest me the best way to design my database.

    - by Raymond Ho
    I have a table named "Pages" and a table named "Categories". Each entry of the table "Pages" is linked to the table "Categories". The "Categories" table have 5 entries, they are: "Car", "Websites", "Technology", "Mobile Phones", and "Interest". So each time I put an entry to the "Pages" table, I need to map it to the "Categories" table so are arranged properly. Here's my table: Pages ______ id [PK] name url Categories ______ id [PK] Categoryname Pages2Categories ______ Pages.id Categories.id So my question is, is this the most efficient way to create this kind of relationships between tables? It seems very amateur

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  • group_concat on an empty join in MySQL

    - by Yossarian
    Hello, I've got the following problem: I have two tables: (simplified) +--------+ +-----------+ | User | | Role | +--------+ +-----------+ | ID<PK> | | ID <PK> | +--------+ | Name | +-----------+ and M:N relationship between them +-------------+ | User_Role | +-------------+ | User<FK> | | Role<FK> | +-------------+ I need to create a view, which selects me: User, and in one column, all of his Roles (this is done by group_concat). I've tried following: SELECT u.*, group_concat(r.Name separator ',') as Roles FROM User u LEFT JOIN User_Role ur ON ur.User=u.ID LEFT JOIN Role r ON ur.Role=r.ID GROUP BY u.ID; However, this works for an user with some defined roles. Users without role aren't returned. How can I modify the statement, to return me User with empty string in Roles column when User doesn't have any Role? Explanation: I'm passing the SQL data directly to a grid, which then formats itself, and it is easier for me to create slow and complicated view, than to format it in my code. I'm using MySQL

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  • SQL not yielding expected results

    - by AnonJr
    I have three tables related to this particular query: Lawson_Employees: LawsonID (pk), LastName, FirstName, AccCode (numeric) Lawson_DeptInfo: AccCode (pk), AccCode2 (don't ask, HR set up), DisplayName tblExpirationDates: EmpID (pk), ACLS (date), EP (date), CPR (date), CPR_Imported (date), PALS (date), Note The goal is to get the data I need to report on all those who have already expired in one or more certification, or are going to expire in the next 90 days. Some important notes: This is being run as part of a vbScript, so the 90-day date is being calculated when the script is run. I'm using 2010-08-31 as a placeholder since its the result at the time this question is being posted. All cards expire at the end of the month. (which is why the above date is for the end of August and not 90 days on the dot) A valid EP card supersedes ACLS certification, but only the latter is required of some employees. (wasn't going to worry about it until I got this question answered, but if I can get the help I'll take it) The CPR column contains the expiration date for the last class they took with us. (NULL if they didn't take any classes with us) The CPR_Imported column contains the expiration date for the last class they took somewhere else. (NULL if they didn't take it elsewhere, and bravo for following policy) The distinction between CPR classes is important for other reports. For purposes of this report, all we really care about is which one is the most current - or at least is currently current. If I have to, I'll ignore ACLS and PALS for the time being as it is non-compliance with CPR training that is the big issue at the moment. (not that the others won't be, but they weren't mentioned in the last meeting...) Here's the query I have so far, which is giving me good data: SELECT iEmp.LawsonID, iEmp.LastName, iEmp.FirstName, dept.AccCode2, dept.DisplayName, Exp.ACLS, Exp.EP, Exp.CPR, Exp.CPR_Imported, Exp.PALS, Exp.Note FROM (Lawson_Employees AS iEmp LEFT JOIN Lawson_DeptInfo AS dept ON dept.AccCode = iEmp.AccCode) LEFT JOIN tblExpirationDates AS Exp ON iEmp.LawsonID = Exp.EmpID WHERE iEmp.CurrentEmp = 1 AND ((Exp.ACLS <= #2010-08-31# AND Exp.ACLS IS NOT NULL) OR (Exp.CPR <= #2010-08-31# AND Exp.CPR_Imported <= #2010-08-31#) OR (Exp.PALS <= #2010-08-31# AND Exp.PALS IS NOT NULL)) ORDER BY dept.AccCode2, iEmp.LastName, iEmp.FirstName; After perusing the result set, I think I'm missing some expiration dates that should be in the result set. Am I missing something? This is the sucky part of being the only developer in the department... no one to ask for a little help.

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  • Querying my JPA provider (Hibernate) for a collection of <Id,Name> of an entity

    - by Ittai
    Hi, I have an entity which looks something like this: Id (PK) Name Other business properties and associations... I have the need for my DAL (JPA with hibernate as provider) to return a list of the entities which correlate to some constraints (or just return them all) but instead of returning the entities themselves I'd like to receive only the Id and the Name properties. I know this can be achieved with HQL/SQL (something like: select id,name from entity where...) but I don't want to go down that road. I was thinking of somehow defining the pair a compositioned part of the entity and thought that might help me but I'm not sure that's "legal" as the Id is the PK. The logic for this scenario is to have a textbox which asynchronously queries the web-service (and through it the DAL) for the relevant entities and once an entity is selected then it is loaded as a whole and shipped to the front-end. Would appreciate any feedback, Ittai

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  • group by with 3 diffrent

    - by NN
    I have 2 table and I wanna a query with 3 column result in on of them 2 column with view count and title name and in the other 1 column with type_ and i wanna to grouping type_ with max(view count) and show the them title but i didn't have any idea about grouping expression. i think we can solve in by using sub query but i don't know which column use in group by. 2 table join with this expression class pk=resource key i exam this query: SELECT t.title,j.type_ FROM tags asset t,journal article j where type_ in (select type_ from journal article,tags asset where class pk=resource key group by type_) but the answer was wrong

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  • Navigating by foreign keys in ADO.NET Entity Framework/MySQL

    - by Werg38
    I am using ASP.NET MVC2 on top of a MySQL database in VS2008. I am using the MySQL ADO.NET connector 6.2.3 to provide the connection for the ADO.NET Entity Data Model. This is mostly working ok, however navigating via foreign keys is causing me a real headache! Here is a simplified example.. Car (Table) CarID PK Colour Doors ManufacturerID FK Manufacturer (Table) ManufacturerID PK Name In the edmx file I can see the 1-many relationship shown as a navigation property in the both the Car and Manufacturer tables. I create a Models.CarRepository that allows me to returns a IQueryable. At the View I want to be able to display the Manufacturer.Name for each car. This is not accessible via the object I get returned. What is best way to implement this? Have I encountered a limitation of the Entity Framework/MySQL combination?

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  • JPA 2.0 Eclipse Link ... Composite primary keys

    - by Parhs
    I have two entities(actually more but it doenst matter) Exam and Exam_Normals Its a oneToMany relationship... The problem is that i need a primary key for Exams_Normals PK (Exam_ID Item) Item should be 1 2 3 4 5 etc.... But cant achieve it getting errors An alternative would be to: I cound use an IDENTITY and a ManyToOne relationship at Exam_Normals but that should be like PK(Exam_Normals_ID) and a reference to Exam and an extra collumn Item to keep an order.. SO 3 collumns But to avoid the alternative tried I tried with @IdClass and got errors Tried @EmbeddedID everything nothing works Any idea??

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  • Django: Data corrupted after loading? (possible programmer error)

    - by Rosarch
    I may be loading data the wrong way. excerpt of data.json: { "pk": "1", "model": "myapp.Course", "fields": { "name": "Introduction to Web Design", "requiredFor": [9], "offeringSchool": 1, "pre_reqs": [], "offeredIn": [1, 5, 9] } }, I run python manage.py loaddata -v2 data: Installed 36 object(s) from 1 fixture(s) Then, I go to check the above object using the Django shell: >>> info = Course.objects.filter(id=1) >>> info.get().pre_reqs.all() [<Course: Intermediate Web Programming>] # WRONG! There should be no pre-reqs >>> from django.core import serializers >>> serializers.serialize("json", info) '[{"pk": 1, "model": "Apollo.course", "fields": {"pre_reqs": [11], "offeredIn": [1, 5, 9], "offeringSchool": 1, "name": "Introduction to Web Design", "requiredFor": [9]}}]' The serialized output of the model is not the same as the input that was given to loaddata. The output has a non-empty pre_req list, whereas the input's pre_reqs field is empty. What am I doing wrong?

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  • Reusing an anonymous parameter in a prepared statement

    - by Chris Lieb
    I am customizing the insert SQL generated by hibernate and have hit an issue. When Hibernate generates the query by itself, it inserts data into the first two columns of the table, but this causes a database error since all four columns of the table are non-nullable. For the insert to be performed properly, it must insert the same data into two columns of the new record. This means that I need Hibernate to bind the same data to two different parameters in the query (prepared statement) that I am writing. Is there some SQL syntax that allows me to refer to anonymous parameters bound to a prepared statement in an order different from which they are bound? Details REF_USER_PAGE_XREF ---------------------------------------- PK FK1 | NETWORK_ID | VARCHAR2(100) PK FK1 | PAGE_PATH | VARCHAR2(1000) | USER_LAST_UPDT | VARCHAR2(100) | TMSP_LAST_UPDT | DATE insert into REF_USER_ROLE_XREF( NETWORK_ID, PAGE_PATH, TMSP_LAST_UPDT, USER_LAST_UPDT) values ( ?, /* want to insert the same data here */ ?, ?, /* and here */ (select to_char(sysdate, 'DD-MON-YY') from dual) I want to insert the same data into the first and third anonymous parameters.

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  • Alter multiple tables' columns length

    - by gdoron
    So, we just found out that 254 tables in our Oracle DBMS have one column named "Foo" with the wrong length- Number(10) instead of Number(3). That foo column is a part from the PK of the tables. Those tables have other tables with forigen keys to it. What I did is: backed-up the table with a temp table. Disabled the forigen keys to the table. Disabled the PK with the foo column. Nulled the foo column for all the rows. Restored all the above But now we found out it's not just couple of tables but 254 tables. Is there an easy way, (or at least easier than this) to alter the columns length? P.S. I have DBA permissions.

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  • SSAS OLAP MDX and relationships

    - by Sonic Soul
    I new to OLAP, and still not sure how to create a relationship between 2 or more entities. I am basing my cube on views. For simplicity sake let's call them like this: viewParent (ParentID PK) viewChild (ChildID PK, ParentID FK) these views have more fields, but they're not important for this question. in my data source, i defined a relationship between viewParent and viewChild using ParentID for the link. As for measures, i was forced to create separate measures for Parent and Child. in my MDX query however, the relationship does not seem to be enforced. If i select record count for parent, child, and add some filters for the parent, the child count is not reflecting it.. SELECT { [Measures].[ParentCount],[Measures].[ChildCount] } ON COLUMNS FROM [Cube] WHERE { ( {[Time].[Month].&[2011-06-01T00:00:00]} ,{[SomeDimension].&[Foo]} ) } the selected ParentCount is correct, but ChildCount is not affected by any of the filters (because they are parent filters). However, since i defined a relationship, how can i take advantage of that to filter children by parent filter?

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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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  • Django: Why Doesn't the Current URL Match any Patterns in urls.py

    - by austin_sherron
    I've found a few questions here related to my issue, but I haven't found anything that has helped me resolve my issue. I'm using Python 2.7.5 and Django 1.8.dev20140627143448. I have a view that's interacting with my database to delete objects, and it takes two arguments in addition to a request: def delete_data_item(request, dataclass_id, dataitem_id): form = AddDataItemForm(request.POST) data_set = get_object_or_404(DataClass, pk=dataclass_id) context = {'data_set': data_set, 'form': form} data_item = get_object_or_404(DataItem, pk=dataitem_id) data_item.delete() data_set.save() return HttpResponseRedirect(reverse('detail', args=(dataclass_id,))) The URL in myapp.urls.py looks something like this: url(r'^(?P<dataclass_id>[0-9]+)/(?P<dataitem_id>[0-9]+)/delete_data_item/$', views.delete_data_item, name='delete_data_item') and the portion of my template relevant to the view is: <a href="{% url 'delete_data_item' data_set.id data_item.id %}">DELETE</a> Whenever I click on the DELETE link, django tells me that the request URL: http://127.0.0.1:8000/myapp/5/%7B%%20url%20'delete_data_item'%20data_set.id%20data_item.id%20%%7D doesn't match any of my URL patterns. What am I missing? The URL on which the DELETE links exist is myapp/(<dataclass_id>[0-9]+)/

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  • Most efficient way to maintain a 'set' in SQL Server?

    - by SEVEN YEAR LIBERAL ARTS DEGREE
    I have ~2 million rows or so of data, each row with an artificial PK, and two Id fields (so: PK, ID1, ID2). I have a unique constraint (and index) on ID1+ID2. I get two sorts of updates, both with a distinct ID1 per update. 100-1000 rows of all-new data (ID1 is new) 100-1000 rows of largely, but not necessarily completely overlapping data (ID1 already exists, maybe new ID1+ID2 pairs) What's the most efficient way to maintain this 'set'? Here are the options as I see them: Delete all the rows with ID1, insert all the new rows (yikes) Query all the existing rows from the set of new data ID1+ID2, only insert the new rows Insert all the new rows, ignore inserts that trigger unique constraint violations Any thoughts?

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  • Storing Values in colunms alphabetic?

    - by Mdillion
    Is there any benefit to storing content alphabetic in columns? Maybe make lookups faster? If yes then when i add new lookup values to my tables do i need to rebuild the PK for the looup values to fit in the new text? Say a table like this: City_tbl city_id: example: 1120 City_name: example: New York. If I need to add Chicago to it, do i add it at the bottom of the list with the next ID which may be 2000 or do i inset it after the city in alphabetic order which would mean I need to update the PK Id of all following IDs by 1. Only benefit I know about is when I have to manually add lookup values without quering the database I can quickly check the lookup value list for exiting items with ease. But not sure if it may make lookups faster or something if the system knows the text is in aplhabetic order.

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  • Next Identity Key LINQ + SQL Server

    - by user569347
    To represent our course tree structure in our Linq Dataclasses we have 2 columns that could potentially be the same as the PK. My problem is that if I want to Insert a new record and populate 2 other columns with the PK that was generated there is no way I can get the next identity and stop conflict with other administrators who might be doing the same insert at the same time. Case: A Leaf node has right_id and left_id = itself (prereq_id) **dbo.pre_req:** prereq_id left_id right_id op_id course_id is_head is_coreq is_enforced parent_course_id and I basically want to do this: pre_req rec = new pre_req { left_id = prereq_id, right_id = prereq_id, op_id = 3, course_id = query.course_id, is_head = true, is_coreq = false, parent_course_id = curCourse.course_id }; db.courses.InsertOnSubmit(rec); try { db.SubmitChanges(); } Any way to solve my dilemma? Thanks!

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  • simple query Delete records in a table based on count logic

    - by user1905941
    a table with a pk and status column which is having values as 'Y','N','NULL' Query: get the count of records with status column as 'Y', if this count exceeds 1% of total count of records then dont delete , else delete the records in the table. i tried like this Declare v_count Number; v_count1 Number; BEGIN v_count := select count(*) from temp; v_count1 := select count(*) from temp where status = 'Y' ; v_count := v_count + ((0.1) * (v_count)) if (v_count1 > v_count) { insert into temp1 values(pk,status) } else { Delete from temp ; } END;

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  • LINQ to SQL and missing Many to Many EntityRefs

    - by Rick Strahl
    Ran into an odd behavior today with a many to many mapping of one of my tables in LINQ to SQL. Many to many mappings aren’t transparent in LINQ to SQL and it maps the link table the same way the SQL schema has it when creating one. In other words LINQ to SQL isn’t smart about many to many mappings and just treats it like the 3 underlying tables that make up the many to many relationship. Iain Galloway has a nice blog entry about Many to Many relationships in LINQ to SQL. I can live with that – it’s not really difficult to deal with this arrangement once mapped, especially when reading data back. Writing is a little more difficult as you do have to insert into two entities for new records, but nothing that can’t be handled in a small business object method with a few lines of code. When I created a database I’ve been using to experiment around with various different OR/Ms recently I found that for some reason LINQ to SQL was completely failing to map even to the linking table. As it turns out there’s a good reason why it fails, can you spot it below? (read on :-}) Here is the original database layout: There’s an items table, a category table and a link table that holds only the foreign keys to the Items and Category tables for a typical M->M relationship. When these three tables are imported into the model the *look* correct – I do get the relationships added (after modifying the entity names to strip the prefix): The relationship looks perfectly fine, both in the designer as well as in the XML document: <Table Name="dbo.wws_Item_Categories" Member="ItemCategories"> <Type Name="ItemCategory"> <Column Name="ItemId" Type="System.Guid" DbType="uniqueidentifier NOT NULL" CanBeNull="false" /> <Column Name="CategoryId" Type="System.Guid" DbType="uniqueidentifier NOT NULL" CanBeNull="false" /> <Association Name="ItemCategory_Category" Member="Categories" ThisKey="CategoryId" OtherKey="Id" Type="Category" /> <Association Name="Item_ItemCategory" Member="Item" ThisKey="ItemId" OtherKey="Id" Type="Item" IsForeignKey="true" /> </Type> </Table> <Table Name="dbo.wws_Categories" Member="Categories"> <Type Name="Category"> <Column Name="Id" Type="System.Guid" DbType="UniqueIdentifier NOT NULL" IsPrimaryKey="true" IsDbGenerated="true" CanBeNull="false" /> <Column Name="ParentId" Type="System.Guid" DbType="UniqueIdentifier" CanBeNull="true" /> <Column Name="CategoryName" Type="System.String" DbType="NVarChar(150)" CanBeNull="true" /> <Column Name="CategoryDescription" Type="System.String" DbType="NVarChar(MAX)" CanBeNull="true" /> <Column Name="tstamp" AccessModifier="Internal" Type="System.Data.Linq.Binary" DbType="rowversion" CanBeNull="true" IsVersion="true" /> <Association Name="ItemCategory_Category" Member="ItemCategory" ThisKey="Id" OtherKey="CategoryId" Type="ItemCategory" IsForeignKey="true" /> </Type> </Table> However when looking at the code generated these navigation properties (also on Item) are completely missing: [global::System.Data.Linq.Mapping.TableAttribute(Name="dbo.wws_Item_Categories")] [global::System.Runtime.Serialization.DataContractAttribute()] public partial class ItemCategory : Westwind.BusinessFramework.EntityBase { private System.Guid _ItemId; private System.Guid _CategoryId; public ItemCategory() { } [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_ItemId", DbType="uniqueidentifier NOT NULL")] [global::System.Runtime.Serialization.DataMemberAttribute(Order=1)] public System.Guid ItemId { get { return this._ItemId; } set { if ((this._ItemId != value)) { this._ItemId = value; } } } [global::System.Data.Linq.Mapping.ColumnAttribute(Storage="_CategoryId", DbType="uniqueidentifier NOT NULL")] [global::System.Runtime.Serialization.DataMemberAttribute(Order=2)] public System.Guid CategoryId { get { return this._CategoryId; } set { if ((this._CategoryId != value)) { this._CategoryId = value; } } } } Notice that the Item and Category association properties which should be EntityRef properties are completely missing. They’re there in the model, but the generated code – not so much. So what’s the problem here? The problem – it appears – is that LINQ to SQL requires primary keys on all entities it tracks. In order to support tracking – even of the link table entity – the link table requires a primary key. Real obvious ain’t it, especially since the designer happily lets you import the table and even shows the relationship and implicitly the related properties. Adding an Id field as a Pk to the database and then importing results in this model layout: which properly generates the Item and Category properties into the link entity. It’s ironic that LINQ to SQL *requires* the PK in the middle – the Entity Framework requires that a link table have *only* the two foreign key fields in a table in order to recognize a many to many relation. EF actually handles the M->M relation directly without the intermediate link entity unlike LINQ to SQL. [updated from comments – 12/24/2009] Another approach is to set up both ItemId and CategoryId in the database which shows up in LINQ to SQL like this: This also work in creating the Category and Item fields in the ItemCategory entity. Ultimately this is probably the best approach as it also guarantees uniqueness of the keys and so helps in database integrity. It took me a while to figure out WTF was going on here – lulled by the designer to think that the properties should be when they were not. It’s actually a well documented feature of L2S that each entity in the model requires a Pk but of course that’s easy to miss when the model viewer shows it to you and even the underlying XML model shows the Associations properly. This is one of the issue with L2S of course – you have to play by its rules and once you hit one of those rules there’s no way around them – you’re stuck with what it requires which in this case meant changing the database.© Rick Strahl, West Wind Technologies, 2005-2010Posted in ADO.NET  LINQ  

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