Attribute
An attribute: a property recorded for each entity, such as a customer’s name or an order’s date. In Chen notation as most database textbooks draw it, an attribute is an oval with its name inside, joined by a line to its entity.
Easily confused with
How to read it
Each oval holds one property, and an entity can have as many as it needs. Relationships can have attributes too: the hours an employee works on a project belong to the pairing, not to either side. Variants of the oval mark kinds of attribute: an underlined name is a Key attribute, a double oval a Multivalued attribute, a dashed oval a Derived attribute, and an oval with smaller ovals hanging from it a composite attribute made of parts, such as an address.
Peter Chen’s 1976 paper defined an attribute as a function from an entity set or relationship set into a value set; the oval convention is the one in Elmasri and Navathe’s textbook and the course notes that follow it.
Also searched as: attribute symbol, er diagram oval.
Look-alikes
A horizontal ellipse in a UML use case diagram is a use case, something an actor does with the system. On a flowchart, a rounded shape at the start or end is a terminal.
Differences by textbook
Silberschatz, Korth and Sudarshan’s Database System Concepts has no attribute ovals: attributes are listed inside the entity rectangle. Crow’s foot diagrams and Richard Barker’s notation do the same.
Read next
- Next in ER diagram symbolsKey attributeA key attribute: the property that identifies each record uniquely, such as an order’s ID number. On a Chen-style ER diagram its name is underlined inside the oval.
- The same shape in AI labels and iconsAI iconAI-generated or AI-changed content. A badge with the letters AI, often in a circle or beside a word such as generated or modified, labels an image, video, sound or text as made or altered with artificial intelligence. The European Union publishes an official set of these icons.
More ER diagram symbols
The same shape elsewhere
Browse symbols drawn with circles or letters and numbers.
Sources
- A Practical Introduction to Databases: 2.2 Entity-relationship diagrams, Christopher Painter-Wakefield, 2022, Runestone Academy, 2.2.1.2 Attributes
- Data Modeling Using the Entity-Relationship (ER) Model (chapter 3 slides), Ramez Elmasri and Shamkant B. Navathe, Fundamentals of Database Systems, 2016, Pearson, course CS 448, Purdue University, Slides 3-18 and 3-40
- The Entity-Relationship Model (database systems course notes), Last updated 6 September 2019, Juniata College, Entities and Attributes
- The Entity-Relationship Model: Toward a Unified View of Data, Peter Pin-Shan Chen, ACM Transactions on Database Systems 1, no. 1 (March 1976): 9–36, Association for Computing Machinery (copy hosted by California State University, Bakersfield), Section 2.2.3, p. 12
- Database System Concepts, 7th edition, chapter 6 slides: Database Design Using the E-R Model, Abraham Silberschatz, Henry F. Korth and S. Sudarshan, db-book.com, Slide 6.12
- Richard Barker (data modeling notations), David C. Hay, 1999, Essential Strategies, Inc., Entities and attributes
Researched, edited and approved by Rory Hansen before publishing. Last reviewed October 9, 2026. How we research
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