What Is Cardinality?

A quick Google search on cardinal will give you: a high ecclesiastical official of the Roman Catholic Church who ranks next below the pope and is appointed by him to assist him as a member of the college of cardinal. Although we are not discussing the same, in principle works in the same manner of application. In database design, cardinality is a big word that has to do with counting tables and values. It has three primary definitions. Cardinality can relate to counting the number of elements in a set. This means, for example, that if you have a table with five columns and ten rows, this is considered a 5-by-10 table (five rows and ten columns). It can identify the relationships between tables. For example, if you have two tables related to one or more fields, they are said to be conveyed by cardinality. This could mean that one table contains all the data from which another table was derived or any other possibilities. It can describe how database tables have several values and what those tables look like. The cardinality between tables can be one-to-one, many-to-one or many-to-many; it all depends on where you're looking at it! It's a simple concept that can have some unexpected consequences. Let's say you have a customer database table, and that table has a one-to-one cardinality relationship with another database table where the customer can store their purchases. Now let's change that setup. Instead of an identification card, the customer has a record of their assets in a secondary database table. There will likely be several purchases for each customer, so in these supplementary tables, the one customer's link to the multiple purchases is a one-to-many cardinality relationship. What does this mean for you? Your search process must consider the number of entries in those supplementary tables before making valuable recommendations about what products might best suit each customer's needs and wants.