The cardinality of the relationship means having unique or multiple instances per value for the joining field between two tables.
Cardinality defined by the relationship. Cardinality refers to the relationship between two tables. Cardinality can be of 3 types
- Many to One
- One to Many
- Many to Many
The cardinality refers to the uniqueness of a columns in a table. The columns with all unique values would be having the high cardinality and the columns with all duplicates values would be having the low cardinality.