This is an ERD for a company with the following details:

1. Company organized into DEPARTMENT. Each department has unique name and a particular employee who  manages the department. Start date for the manager is recorded. Department may have several locations.
2. A department controls a number of PROJECT. Projects have a unique name, number and a single location.
3. Company’s EMPLOYEE name, ssno, address, salary, sex and birth date are recorded. An employee is assigned to one department, but may work for several projects (not necessarily controlled by her dept). Number of hours/week an employee works on each project is recorded; The immediate supervisor for the employee.
4. Employee’s DEPENDENT are tracked for health insurance purposes (dependent name, birthdate, relationship to employee).

Consider a university database for the scheduling of classrooms for final exams. This database could be modeled as the single entity set exam, with attributes course-name, section-number, room-number, and time. Alternatively, one or more additional entity sets could be defined, along with relationship sets to replace some of the attributes of the exam entity set, as:

1. course with attributes name, department, and c-number
2. section with attributes s-number and enrolment, and dependent as a weak entity set on course
3. room with attributes r-number, capacity, and building

This is an ER diagram example that illustrates the use of all three additional entity sets listed.

This is an ER diagram example that shows the major business entities of an online bookstore as well as their inter-relationships. It consists of typical entities like Book, Author, Publisher, Customer, etc.

This E-R diagram example keeps track of the exploits of your favorited sports team. The database design stores the matches played, the scores in each match, the players in each match and individual player statistics for each match. Summary statistics is modeled as derived column with the use of a stereotype.

Here are two versions of an ERD for marks database.

a) Consider a database used to record the marks that students get in different exams of different course offerings. This E-R diagram models exams as entities, and uses a ternary relationship, for the above database.

B) This is an alternative ER diagram (ERD) that uses only a binary relationship between students and course-offerings. Make sure that only one relationship exists between a particular student and course-offering pair, yet you can represent the marks that a student gets in different exams of a course offering.

This is an E-R diagram (ERD) example for a hospital with a set of patients and a set of medical doctors. Each patient is associated with a log of the various tests and examinations conducted.

This is an E-R diagram example for a car-insurance company whose customers own one or more cars each. Each car has associated with it zero to any number of recorded accidents.

This ERD example models the following information.

1. A Course has an ID (for unique identification), syllabus, title, credits and prerequisites.
2. A Student has an ID (for unique identification), name, and program.
3. An Instructor, has an ID (for unique identification), name, department, and title.
4. A Student may enrol into one or more Courses, while an Instructor teaches one or more Courses. Course Offering, the linked entity has a time (of course), section no., room id, year and semester.

Suppose you are given the following requirements for a simple database for the National Hockey League (NHL):

1. The NHL has many teams, each team has a name, a city, a coach, a captain, and a set of players,
2. Each player belongs to only one team, each player has a name, a position (such as left wing or goalie), a skill level, and a set of injury records,
3. A team captain is also a player,
4. A game is played between two teams (referred to as HostTeam and GuestTeam) and has a date (such as Jun 12th, 2017) and a score (such as 4 to 2)

This ERD example shows a clean and concise ER diagram for the NHL database.