i have a problem with inserting data in my database.
I have three tables which i created with the heideSQL and linked the three tables with foreign key. 1st table (many to one) 2nd table (one to many) 3rd table. when i try now to insert new data with db.SaveChanges(); it throws an insert exception which tells me that he cant match the foreign key because eventually two or more objects have the same primary key. but i just have one ID-Field in each table which is AUTO_INCREMENT. i use the ID-Field of the 2nd table to link in the first and the 3rd one.
could the problem be that everytime i create the new database object for insert that i always add the same object which belongs to the 2nd table to the db-object even it stays the same. same with the object for the 1st table. might that be the mistage and how can i fix this?
the code and the pic of the database are attached. i hope it helps to understand my problem.
Cheers, Only3lue
db.zeichnungs.Add(zeichnung);
db.projekts.Add(projekt);
db.tags.Add(tag);
}
try
{
db.SaveChanges();
} ...
Related
I have related tables in SQL (one to many). One is employees table and the other is the record table for day offs, When i want to delete one employee I get the below error in C#:
SqlException: The DELETE statement conflicted with the REFERENCE constraint "FK_Izin_Personel". The conflict occurred in database "Inotra", table "dbo.Izin", column 'personelid'.
The statement has been terminated.
I tried changing insert and update actions to cascade and that worked for other tables, but it also deletes from both tables when I delete from one.
So my question is: How can I remove from only one of the two related tables, so that the records of other table remain unchanged?
When you delete from the employee table, then you must also delete all related records in the record table.
Relationships ensure data integrity, without them, data may be incomplete or incorrect. In your case you need to remove the relationship between the tables("FK_Izin_Personel"), then there will be no error.
In my database, I have a parent table and a child table with foreign key pointing to the parent.. at some point I have to clear all rows from both tables.
I used the following code in Entity Framework:
using (MuseumDBEntities db = new MuseumDBEntities())
{
db.Database.ExecuteSqlCommand("truncate table childTable");
db.Database.ExecuteSqlCommand("truncate table parentTable");
}
I get an exception at the second truncate because of foreign key, although I am clearing child table first.
What should I do? Is there another way to delete all rows of both tables?
I don't know if a foreach loop over all rows is practical.
That's SQL server's fault!
You have two ways to achieve your goal:
Drop the foreign keys, then truncate the table and then recreate the foreign key (I don't recommend this solution because it is too much work and usually not worth it)
Instead of Truncate use Delete (I usually use this method)
Your code will look like this:
using (MuseumDBEntities db = new MuseumDBEntities())
{
db.Database.ExecuteSqlCommand("Delete from childTable");
db.Database.ExecuteSqlCommand("Delete from parentTable");
}
Since the two delete statements have no conditions (no where clause), all rows will be deleted from the tables.
I have two tables that are basically link tables.
So one looks like this;
QueueId
TaskId
the two columns link to a Queues table and a Tasks table.
There is no primary key and i don't believe I need one.
I so try to import it into my .EDMX and I get the warning that
the table does not have a primary key defined but that it's been inferred as a read only table.
Also, the table doesn't show up in the Diagram and there is no model created for it.
I added a primary key and then got errors in my code.
I deleted all tables and did it all again and still the same thing happens with this one table.
The second table that is virtually identical has the same error but does appear in the diagram.
How do I get the first table to show in the diagram and not be read only because I need to delete the associations from time to time.
Thanks
Entity Framework doesn't need association table in the model to work with it.
There should be two navigation properties on either side of the relation - Task has ICollection<Queue> and Queue has ICollection<Task>. To remove association between specific task and queue you either find queue and remove that thask from it's collection, or do the reverse.
I am using MYSql database and Entity Framework as an ORM to it.
I have two tables:
table A and table B. Table A has a field which is a foreign key on some field from table B.
And the constraints to this key are: Update:Restrict, Delete:Restrict
So the situation:
when I try to delete a record from table B everything works fine
when I try to delete a record from table B and this record is referenced by another record from table A it does nothing and it is expected ofc.
when I try to delete a record from table B, which is referenced, it does nothing but if I after this try to delete a record from table A which was referencing that record from table B it appears that both records are deleted. But only the record from table A should be deleted.
So I assume that there is some kind of caching which caches the unsuccessfull query and tries to execute it when possible.
In some time I`ll try to post some pictures if my words are very fuzzy =)
Ah, and the question: can anyone clear this situation?)
Resolved this issue.
No caching or such things =)
Just entity object which I tried to delete was marked with EntityState.Deleted and despite the exception throwed the state wasn`t rollbacked.
I'm using ADO.NET with a strongly typed dataset in C# (.NET 3.5). I want to insert a new row to two tables which are related in an 1:n relation.
The table Attachments holds the primary key part of the relation and the table LicenseAttachments holds the foreign key part.
AttachmentsDataSet.InvoiceRow invoice; // Set to a valid row, also referenced in InvoiceAttachments
AttachmentsDataSet.AttachmentsRow attachment;
attachment = attachmentsDataSet.Attachments.AddAttachmentsRow("Name", "Description");
attachmentsDataSet.InvoiceAttachments.AddInvoiceAttachmentsRow(invoice, attachment);
Of course when I first update the InvoicesAttachments table, I'll get a foreign key violation from the SQL server, so I tried updating the Attachments table first, which will create the rows, but will remove the attachment association in the InvoiceAttachments table. Why?
How do I solve this problem?
On the relation between the tables, ensure that the "Both Relation and Foreign Key Constraint" is selected and "Update Rule" is set to "Cascade". Combined with the "Refresh the data table" option on the adapter, after you insert your parent row, the updated ID will "Cascade" down the relationships, preventing foreign key violations in your dataset. Your child tables will then be ready to properly insert into the database.
Some things to try:
When you configure the tableadapter, did you click on advanced options, and check on "refresh data table" so that it will retrieve the identity column value?
For me sometimes I either forgot to check it, or it didn't save the configuration correctly because I didn't have my table identity increment/seed set for whatever reason. Are you using identity increment on the table?
You might also consider just re-creating the adapters for those two tables.
Usually when I go back over everything I find it was something stupid on my part.
Lastly, you might consider calling update on the Primary table, then manually grab the primary key value and manually set the value when you insert the child record. If that doesn't make sense let me know and I will post code.
You need to tell your parent table's table-adapter to refresh the
data-table after update operation.
This is how you can do that.
Open the properties of ProgramUserGroupTableAdapter -> Default Select Query -> Advnaced options. and Check the option of Refresh the data table. Save the adapter now. Now when you call update on table-adapter, the data-table will be updated [refreshed] after the update operation and will reflect the latest values from database table. if the primary-key or any coloumn is set to auto-increment, the data-table will have those latest value post recent update.
Now you can Call the update as pug.Update(dsUserGroup.ProgramUserGroup);
Read latest values from the ProgramUserGroup coloumns and assign respective values into the child table before update. This will work exactly the way you want.
alt text http://ruchitsurati.net/files/tds1.png