Foreign keys and NULL in mySQL
- by Industrial
Hi everyone,
Can I have a column in my values table (value) referenced as a foreign key to knownValues table, and let it be NULL whenever needed, like in the example:
Table: values
product type value freevalue
0 1 NULL 100
1 2 NULL 25
3 3 1 NULL
Table: types
id name prefix
0 length cm
1 weight kg
2 fruit NULL
Table: knownValues
id Type name
0 2 banana
Note: The types in the table values & knownValues are of course referenced into the types table.
Thanks!
