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'