All Questions
Tagged with hierarchy foreign-key
6 questions
2
votes
3
answers
1k
views
Foreign key reference to column that is no primary key
I know, foreign keys should uniquely identify rows and therefore reference a primary key.
However, consider my example: There are 4 pre-defined categories, and for some combinations of values for ...
- 121
2
votes
0
answers
56
views
Design for a child to have a single parent `A` OR `B` with FK cascade constraint?
I'm assuming this is not possible with PK and FK...
Let's say I have tables A, B, and C.
A and B are "parents", and B and C are "children"
A is the root
B can be the child of either A or B
C ...
- 121
1
vote
1
answer
110
views
How to add foreign key in a table where column value can come from two different tables?
I have three tables
create table main_comments (
id serial primary key,
comment text not null
);
create table sub_comments (
id serial primary key,
main_id integer not null,
comment ...
- 113
4
votes
1
answer
1k
views
Surrogate vs composite key in hierarchical data structure
I'm currently evaluating a schema for a hierarchical data structure. My main problem is how I should design the schema to prevent inconsistent data (reference of foreign key in another hierarchy). The ...
- 173
7
votes
2
answers
2k
views
Nested table hierarchy: foreign key duplication vs. join
I have a nested table hierarchy, similar to the following one (this is an example but demonstrates the schema well enough):
+---------+ +---------+ +---------+ +-------------+
| users | | ...
- 214
4
votes
1
answer
3k
views
Foreign key with multiple table options
I'm not sure if the title is very good, feel free to suggest a better one.
People can "comment" on different objects of my site,similarly to StackExchange (for example they can comment on a Question, ...
- 313