Simplified ERD is designed for fast writing (drawing?) of ERD ideas and is based on Crow’s Foot ERD, but with these key differences:

  • The arrow heads are easier to remember
  • There aren’t redundant / badly described arrow heads
  • A full entity definition isn’t required

Arrow Heads

Symbol Description / Designation
---|O zero or one
--||O zero or more
----| exactly one
---|| one or more

Examples

Example 1

  • Users each have exactly one language
  • Languages can each have many users
user O||----| language

Example 2

  • Users each have at least one email address
  • Email addresses each have at most one user
user O|----|| email_address