foreign-key-relationship

oracle sql: not able to add foreign key to table -> invalid identifier?

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问题 First off, I'm a real newbie to db and sql. However, I have to tables, PERSON and SPECIES and I want to add a foreign key to the table SPECIES. When trying to add the foreign key I always get the error message "ORA-900904: invalid identifier". I just can't figure out what I've done wrong and why it doesn't work?!?! This was my approach: PERSON table and primary key create table person ( name varchar2 (30), firstname varchar2 (30), persid number (8) not null ) ; alter table person add

how to search filter multipe relation table and groupping in yii2

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问题 I have three tables like ridersPoint (id, nameRider, serie_id, point) and series (serie_id, nameSerie, location, date, season_id) and season (season_id, nameSeason, year) . Attribute serie_id in riderPoint table have relation with serie_id in series table, and Attribute season_id in series table have relation with season_id in season table. How to make search by season_id in riderPoint ? And how to groupping point when have data table in the same season ? Please help me.. 回答1: Search (filter

Can not delete or modify or see same table foreign key constraint

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问题 A same table foreign key constraint in my database is not accessible. I can not drop it, disable it, add it back, ... How do I remove it and re-add it? Note: I have several versions of my database all created with the same script. Only in one I see this behavior. In others, this key is easily added and removed. Many thanks. Here is some scripts I ran and the result: At some point in the past i ran the following script: ALTER TABLE Recipe ADD CONSTRAINT FK_Recipe_DuplicateOfRecipeId_Recipe_Id

How to describe multi-column foreign key in Doctrine mapping

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问题 We have a database schema that, in simplified (slightly contrived) form, looks like: Where the foreign key from users to domains is set on columns (domainId, groupId), to guarantee referential integrity. This structure works fine for the intended purpose. However, for a new application talking to the same database, I now need to create a mapping for Doctrine that maps the above structure, including the Foreign Key relation on two columns. I've tried the following: <entity name="User" table=

Entity Framework 4, inserting with foreign key value not ID

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问题 This is pretty basic question I am sure but it's baffling me now :S I have 2 tables, Students and Courses with a foreign key constraint, Many Students to 1 Course. I store in my Students table a CourseId_FK reference, so when I am creating a Student how would I be able to do something like this? Students student = new Students(); student.Name = Bob; student.Course.CourseName = "Geography"; db.SaveChanges(); Right now, the above doesn't work and I have to resolve to student.CourseId = 22; Can

Django Generic Foreign keys - Good or Bad considering the SQL performance?

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问题 I have a model A which contains a generic foreign key relation with limit choices to 3 other models(consider them as B , C and D ) in the same app. And I know the limitations of generic foreign keys that we can't use filter or get or anyother queryset operations. So to achieve something like this, A.objects.filter(generic_object__name="foo") I have to filter B, C and D's objects first as queryset, iterate over them and use the generic reverse relation to get the A objects as list(not queryset

How to make two foreign keys to same model unique together?

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问题 Let's say I have a relationship class such as: class Friendship(models.Model): person1 = models.ForeignKey(Person, related_name='person1') person2 = models.ForeignKey(Person, related_name='person2') so I want to make this object unique for a pair of Person s. If I simply do unique_together = (("person1", "person2"),) then I can end up with two Friendship objects where FS1.person1 = A, FS1.person2 = B FS2.person1 = B, FS2.person2 = A I do not want this. I want a unique friendship object

oracle sql: not able to add foreign key to table -> invalid identifier?

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First off, I'm a real newbie to db and sql. However, I have to tables, PERSON and SPECIES and I want to add a foreign key to the table SPECIES. When trying to add the foreign key I always get the error message "ORA-900904: invalid identifier". I just can't figure out what I've done wrong and why it doesn't work?!?! This was my approach: PERSON table and primary key create table person ( name varchar2 (30), firstname varchar2 (30), persid number (8) not null ) ; alter table person add constraint person_pk primary key (persid) ; SPECIES table and primary key create table species ( speciesnamelat

Should a two-to-many data relationship be treated as many-to-many?

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问题 I have 2 database tables: Teams and Games. For the purpose of this question, we are dealing with football (soccer) teams and games. Each Game has exactly 2 teams, generally a home team and an away team although occasionally both teams can be neutral. My question is whether I should represent this data relationship using 2 foreign keys in the Games table (home_team_id, away_team_id) or whether I should use a many-to-many relationship with a games_teams table to link the two, in which case I

One-to-One relationship in MS Access

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I'm having trouble in creating a one-to-one relationship between two tables in MS Access - when I create the relationship, it defaults to "Many-to-one", and I don't see an option to change it. Is there a way to do this? Access has no such concept. You can either conflate the two tables into one, or place unique indexes on both tables for the common field(s). Are there other benefits you would expect? You could I suppose create FK relationships in both directions, but I'm not sure what it would gain you except maybe query hints. EDIT: Important update note from comment - I don't see the problem