One-to-many (1:M). The most widely recognized kind of relationship cardinality is a 1:M relationship. Think about the relationship between the Representative and Division.
Data is sorted out in a social database as tables — two-dimensional lattices made up of segments and lines. A table's primary key , authorized by a primary key limitation (which will be characterized in a future article in this arrangement), is a segment or mix of sections that guarantees that each line in a table is exceptionally distinguished. Two tables that have a typical segment are said to have a relationship between them; the normal section is the remote key in one table and the primary key in the other. The value (assuming any) put away in succession/segment mix is a data component.
The cardinality of a relationship is the proportion of the number (additionally called events) of data components in two tables' connected column(s). Relationship cardinality can be of three kinds: one-to-many, one-to-one, or many-to-many.