2.01 Relational Model

relational database

• A database model is a conceptual framework for database systems, with three parts

  • Data Structures

  • Operations

  • Rules

Data Structures

• that prescribe how data is organized.

  • (blank) form the backbone of efficient and organized information storage.

  • Each database model relies on specific structures to represent entities, attributes, and relationships, ensuring data integrity and facilitating smooth retrieval and manipulation.

  • e.g. relational model: primary key, foreign key, data types(INT, STRING, ...), indexes.

set

• unordered collection of elements enclosed in braces.

• e.g. {a, b, c} and {c, b, a} are the same, since sets are not ordered.

tuple

• ordered collection of elements enclosed in parentheses.

• e.g. (a, b, c) and (c, b, a) are different, since tuples are ordered.

table

• has a name, a fixed tuple of columns, and a varying set of rows.

• Synonyms: File, Relation.

column

• name and a data type.

• Synonyms: Field, Attribute

row

• is an unnamed tuple of values. Each value corresponds to a column and belongs to the column's data type.

• since (blank) are a set, (blank) have no inherit order.

• Synonyms: Record, Tuple

relational data type

named set of values, from which column values are drawn.

relational algebra

These operations are collectively called (blank) and are the theoretical foundation of the SQL language.

Relational rules

• (blank) are logical constraints that ensure data is valid.

• are part of the relational model and govern data in every relational database.

SELECT

selects a subset of rows of a table.

JOIN

combines two tables by comparing related columns.

UNION

selects all rows of two tables.

AGGREGATE

computes functions over multiple table rows, such as sum and count.

business rules

based on business policy and specific to a particular database.

Operations

that manipulate data structures.

Rules

logical constraints that ensure the data is valid.