# Relational Model Concepts – Databases and SQL for Data Science by IBM #11 Hello, and welcome to Relational Model Concepts. In this video, we will learn the history of the relational model and some relational terms. At the end of this video, you will be able to define the relational terms, relation, degree and cardinality, and explain the difference between a relational schema and a relational instance. The relational model was first proposed in 1970, and is based on a mathematical model and mathematical terms. The building blocks of the relational model are relation and sets. The relational model of data is based on the concept of relation. A relation is a mathematical concept based on the idea of sets. A set is unordered collection of distinct elements. It is a collection of items of the same type. It would have no order and no duplicates. A relational database is a set of relations. A relation is also the mathematical term for a table. A table is a combination of rows and columns. A relation is made up of two parts, relational schema and relational instance. A relational schema specifies the name of a relation and the attributes. The example here is the entity author. Author is the name of the relation. Author_ ID is an attribute which can hold the data type char, which is a character string of a fixed length. Likewise, lastname, firstname, email and city have the data type varchar, which is a character string of a variable length. The last attribute country, also has a data type of char. This constitutes the relational schema. A relational instance is a table made up of the attributes or columns and the tuples or rows. The columns are the attributes or fields. The rows are tuples. Degree refers to the number of attributes or columns in a relation. Cardinality refers to the number of tuples or rows. In this example, the degree is six because there are six columns, and the cardinality is five because there are five tuples or rows. You’ve heard a lot of new terminology in this session. Let’s review them. The relational model of data is based on the concept of relation. A relation is a mathematical concept based on idea of sets and is the mathematical term for a table. A relation is made up of two parts, relational schema and relational instance. A relational schema specifies the name of a relation and the attributes. A relational instance is a table made up of the attributes or columns and the tuples or rows. Degree refers to the number of attributes or columns in a relation. Cardinality refers to the number of tuples or rows in a relation. You can now define the relational terms relation, degree and cardinality, and explain the difference between a relational schema and a relational instance. Thanks for watching this video. 