many-to-many

I'm an NHibernate developer trying to give Entity Framework a shot in a hobby project. I'm used to specifying mapping data in code using Fluent NHibernate. Pardoning Microsoft's belief that developers shouldn't be allowed to write code, I'm trying to create my mappings using the Entity Framework's visual designer surface (which you get by opening the .edmx file in Visual Studio). I have no idea how to set up a many-to-many relationship! I have 'updated the model' from the database, but I get two one-to-many relationships with a new entity corresponding to the junction table (which contains

I have a data model with a many-to-many relationship like EntityA <-->> EntityB <<--> EntityC . I used to query EntityA with different search criteria and I use NSCompoundPredicate with an array of NSPredicate s. On one of the predicate I wanted to query EntityA using EntityC . I tried to use the following SUBQUERY but it did not work. searchPredicate=[NSPredicate predicateWithFormat:@"(0 != SUBQUERY(EntityB, $B, (0 != SUBQUERY($B.EntityC, $EntityC, $EntityC.name like %@).@count)).@count)", name] And I got the following exception, Terminating app due to uncaught exception

I'm trying to simplify a database structure, and I have two tables matches and team_statistics : Here in the team_statistics table the team_statistics.team_id should be a foreign key that references matches.teams_id and matches.teams_id1 and similarly team_statistics.group_id should be a foreign key referencing matches.groups_id and matches.groups_id1 How to do this in PostgreSQL? If there are other ways of doing this by having another table between matches and team_statistics I'm open for suggestion, but I would still like to know how to have one foreign key referencing two primary keys.

I'm working with a legacy database where FK's aren't always used. For example I have an entity Person and an entity Country. A person has a Country which is mapped as a many-to-one in the Person mapping. <many-to-one name="Country" class="Country" foreign-key="none" lazy="false" not-found="ignore" fetch="join" outer-join="true" column="countryid"/> When person has null as column value (countryid) it won't perform an extra select query (because it knows that there won't be a reference in the country table), but when a person has 0 as column value NH will perform another select to check the

I try to recuperate data from association ManyToMany but i can't, this is my code. Entity Produit : @Entity public class Produit implements Serializable { @Id @Column(name="Produit_ID") @GeneratedValue private Long id; private String dq; private String icForme; private String ich; private String icht; @ManyToMany(cascade = {CascadeType.ALL}) @JoinTable(name="produit_terminal", joinColumns={@JoinColumn(name="Produit_ID")}, inverseJoinColumns={@JoinColumn(name="Terminal_ID")}) private Set<Terminal> terminals = new HashSet<Terminal>(); //getter setter Entity Terminal : @Entity public class

I have the following Many to many relationship (See the picture below) in my SQL server. In most cases there's are 2 rows in table tblWavelengths related to the table tblSensors, (in some cases only 1, and in extreme cases there can be 20 rows) I made the following simple query to retrieve the data from those 3 tables : select W.DateTimeID,S.SensorName,S.SensorType,W.Channel,W.PeakNr,W.Wavelength from tblWavelengths as W Left Join tblSensorWavelengths as SW on W.tblWavelengthID = SW.WavelengthID Left Join tblSensors as S on SW.SensorID = S.SensorID order by W.DateTimeID After running this