I have a junction table with and idenity primary key columns to realize a many to many relationship. Visual Studio automatically detects it as a many to many relationship and the junction table is not an entity.
How can i realize it that also this table is generated as an entity? I need this for breeze.js .
You just need to add additional columns (or properties) to that table (or model).
You said that your table has acolumn named ID and it's the primary key withe IsIdentity set to true. It must works, I'm using this approach...
There must be a problem or missing with your table definition. However, if all are OK, just add a nullable column in your table and update your model from database. The problem will go away.
Related
I'm new to DBIC. I've imported data into a database. It's not possible to create relationships between the tables because, apparently, not all the values in the child table's foreign key column have a corresponding value in the parent table.
So is it possible to still do joins between the tables? I've skimmed through the tutorial and documentation but found nothing that addresses this problem.
You can of course define relationships in your DBIC schema that don't have a matching constraint in the database.
If you use $schema->deploy it will automatically generate constraints for all foreign key columns.
I'm brand new to MySQL Workbench and a have a bit of experience with databases (MS Access). I'm having trouble populating my fk with data. Here's what I have in my db schema:
2 tables Block and Set (Block having a pk Block_ID (type of INT); Set having fk to Block with fk name Set_Block_ID (type of INT).
1 to many relationship created from Block to Set tables linking Block_ID to Set_Block_ID. Relationship created, no problems
I populate the Block table with data. No problems
I then go to populate the Set table with data. I can see all my columns but not the fk. My question is why?
I have created the exact same db in MS Access and my fk is displayed in the linked table and I can populate it while MS Access makes sure referential integrity is enforced. I'm really brand new to Workbench and cant figure out why I cant see and populate my fk column.
Any help is appreciated!
Thanks!! =)
After having digested all the replies to my question (note sarcasm here) I have finally found a workaround way of solving the issue. To recap:
ISSUE:
created a simple 2 table relationship with Workbench with PK and FK (1 .. n relationship)
FK column not visible in Table Edit so not possible to enter any referencing data
SOLUTION:
installed SQLyog and connected to same server
opened same database and redid the simple 1 .. n relationship
FK column visible for editing in SQLyog
likewise, FK column visible for editing in Workbench
As I said, I'm new to this whole thing so I don't know what the problem was in Workbench. I just know it seems to be working fine now.
As you have noticed, the relationship drawing tool does not create actual foreign key constraints.
However, if double-click the referencing table and switch to the foreign-key tab, you can create references and specify the columns involved. This generates and maintains the visual linkage automatically:
I would like to map all many-to-may relations through a single table in my database.
Meaning that I have numerous tables (entities) that have various many-to-many relations. Instead of having a separate mapping table for every relation I would like to use one "master mapping" table having to columns: End1Id & End2Id.
Don't ask why ;) It's required by my customer...
How would I set this up in the model designer, or do I have to edit the edmx xml directly....or is it just not possible?
Thanx for your help!
In such a scenario you can't have explicit foreign keys, because a table like this normally has at least three rows:
PK of table 1
PK of table 2
Type of mapping, which specifies the exact tables to use.
Because of that, you can just create a table in EF, but it will also have no connections to other tables and you will have to do the joins manually.
You would need to set this Master Mappings table manually. The designer doesn't do it for you automatically.
However - if denormalized entities are what you are looking for, better have those denormalized in DB level rather than in EF/code level.
I am using Entity Framework and I ran into an odd build error.
I am building a forum and I set up a table in the database for "ignores" when people don't like each other they will ignore someone. The table has two columns and together they are the primary keys.
PK InitiatingUser
PK IgnoredUser
When EF maps this table I get this error:
Error 7 Error 3034: Problem in mapping fragments starting at lines 1467, 1477:Two entities with possibly different keys are mapped to the same row. Ensure these two mapping fragments map both ends of the AssociationSet to the corresponding columns.
I opened up the edmx in the XML editor and navigated to the offending lines.
<MappingFragment StoreEntitySet="Ignores">
<ScalarProperty Name="IgnoredUser" ColumnName="IgnoredUser" />
<ScalarProperty Name="InitiatingUser" ColumnName="InitiatingUser" />
</MappingFragment>
I am just getting started with EF and I don't understand what is going on or what the issue might be.
Edit
The relationships between ignores used to have foreign keys mapping both initiating user and ignored user to the primary key (username) of users table. That was how it was when I first mapped EF to this table. I have since deleted the FKs to see if that would help but it didn't.
This is likely due to including a many-to-many join table in your entity model, or what EF thinks is such a table (possibly such as one that doesn't have its own self-contained key, but whose identity is made up of two or more foreign keys).
So, for example, let's say you have the following tables:
Person
Address
PersonAddress (contains only PersonID and AddressID)
In your entity model, you should only add Person and Address. If you add PersonAddress, then EF will throw the error. According to this MSDN Q&A, EF will take the join table into account automatically.
I don't know what was wrong here, but I just deleted the table from the ORM and the DB then recreated it with an actual ID column, instead of two primary keys. I re-mapped the table, compiled, and all is well now. It would have been convenient to do it the way I had it, but oh well.
If anyone has any insight let me know. I'd rather accept someone else's answer.
PK InitiatingUser;
PK IgnoredUser
two primary key cannot allow edmx file.so create sno column in that table and make that as primary key . remove the pk of InitiatingUser and IgnoredUser.
now in that two column there is no primary key available.
like
Pk sno;
FK InitiatingUser;
FK IgnoredUser
I'm evaluating using EF against an existing schema - the problem is that I can't work out how to set up associations between tables where the foreign key is NOT the primary key of the master table.
As an example, a foo may have many bars as defined like this (forgive the pseudocode):
table foo {
int foo\_id pk,
char(10) foo\_code,
...
}
table foobar {
int bar\_id pk,
char(10) bar\_foo\_code fk(foo.foo\_code),
...
}
What am I missing to be able to create the foo_foobar association, and hence a Bars navigation property on the Foo entity?
Linq to entities doesn't support Foreign Keys which don't point to the primary key of a table (see log message 3). Linq to entities will treat it as a normal field on a table. You won't be able to navigate to the entity it's linked to.
If you have an existing schema i'd recommend using the edm generator as this will create the EMDX file, code behind and even the view code (which can be very large). If your existing scheme is quite large Check out this post, which explains how to deal with large schemas.
When you run the EDM Generator you'll find out all the things that are not supported.
Looking at a previous EDMGen2.exe log we got the following types of messages back:
The data type 'sql_variant' is not
supported, the column 'ColumnName'
in table 'TableName' was
excluded.
The table/view 'tableName' does not
have a primary key defined. The key
has been inferred and the definition
was created as a read-only table/view
The relationship 'RelationshipName'
has columns that are not part of
the key of the table on the
primary side of the relationship
which is not supported, the
relationship was excluded.
We've also found that the Linq project actually crashed Visual Studio quite alot as the code file produced by EDM was well over 80 mb.