Software & Apps MS Office One-to-One Relationships One-to-one relationships are an integral part of building a database by Mike Chapple Writer Former Lifewire writer Mike Chapple is an IT professional with more than 10 years' experience cybersecurity and extensive knowledge of SQL and database management. our editorial process Twitter Mike Chapple Updated on September 11, 2020 Tweet Share Email MS Office Word Excel Powerpoint Outlook One-to-one relationships occur when there is exactly one record in the first table that corresponds to one record in the related table. For example, U.S. citizens have a Social Security number. Only one number allocates per person. The tables below feature a one-to-one relationship because each row in the first table is directly related to another row in the second table. alexsl / Getty Images Employee Number First Name Last Name 123 Rick Rossin 456 Rob Halford 789 Eddie Henson 567 Amy Bond So the number of rows in the employee names table matches the number of rows in the employee positions table. Employee number Position Phone Ext. 123 Associate 6542 456 Manager 3251 789 Associate 3269 567 Manager 9852 Another type of database model is the one-to-many relationship. Using the bottom table you can see that Rob Halford is a manager, so his relationship to the position is one-to-one because at this company a person only has one position. But the manager position includes two people, Amy Bond and Rob Halford, which is a one-to-many relationship. One position, many people. Was this page helpful? Thanks for letting us know! Get the Latest Tech News Delivered Every Day Email Address Sign up There was an error. Please try again. You're in! Thanks for signing up. There was an error. Please try again. Thank you for signing up. Tell us why! Other Not enough details Hard to understand Submit More from Lifewire One-to-Many Relationships in a Database What Is Transitive Dependency in a Database Entity-Relationship Diagram Definition Creating Database Relationships in Access Introduction to Database Relationships Putting a Database in First Normal Form What Is a Database Relationship? How to Create a Gantt Chart in Google Sheets How to Create a Database in Excel What Is a Database Schema? Determinants and Their Role in a Database What Are Database Dependencies? A Database Attribute Defines the Properties of a Table Databases for Beginners What Is a Database Instance? What Is a Database?