sql - How to store a list in a db column

Question

I would like to store an object FOO in a database. Lets say FOO contains three integers and a list of "Fruits".

The list can have any length, the only thing I know is that the all the fruits allowed are stored in another table.

Can I store the fruit list in a column?

Answer 1

In a normalized relational database, such a situation is unacceptable. You should have a junction table that stores one row for each distinct ID of the FOO object and the ID of the Fruit. Existence of such a row means the fruit is in that list for the FOO.

CREATE TABLE FOO ( 
  id int primary key not null,
  int1 int, 
  int2 int, 
  int3 int
)

CREATE TABLE Fruits (
  id int primary key not null,
  name varchar(30)
)

CREATE TABLE FOOFruits (
  FruitID int references Fruits (ID),
  FooID int references FOO(id),
  constraint pk_FooFruits primary key (FruitID, FooID)
)

To add Apple fruit to the list of a specific FOO object with ID=5, you would:

INSERT FOOFruits(FooID, FruitID)
SELECT 5, ID FROM Fruits WHERE name = 'Apple'