In this post, we will understand the difference between cardinality and modality −
Cardinality
It tells about the maximum number of associations between rows of tables.
There are different types: One-to-one, one-to-many, many-to-many.
One to one is where the occurrence of object ‘A’ can relate to one and only one occurrence of object ‘B’, and vice-versa.
One to many is where the occurrence of object ‘A’ can relate to multiple occurrences of object ‘B’, but object ‘B’ can relate to a single occurrence of object ‘A’.
Many to many is where multiple occurrences of object ‘A’ can relate to multiple occurrences of object ‘B’, and vice-versa.
Modality
It tells about the minimum number of row associations in a table.
There are different types: Nullable and Not nullable.
Nullable columns accept an empty field.
The non-nullable column doesn’t accept null values.