How To Software One-to-One Relationships One-to-one relationships are an integral part of building a database Share Pin Email Print alexsl / Getty Images Software Databases Documents Spreadsheets Presentations Desktop Publishing Graphic Design Animation & Video by Mike Chapple Former Lifewire writer Mike Chapple is an IT professional with more than 10 years' experience cybersecurity and extensive knowledge of SQL and database management. Updated October 11, 2019 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. 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. Learn more about Database Relationships, Foreign Keys, JOINs and E-R Diagrams. Continue Reading Understanding the Types of Database Relationships A Quick Guide to Understanding Database Dependencies How to Establish a One-To-Many Relationship Between Database Tables How to Maintain Relationships in Microsoft Access 2013 Relationships Are the Basis for Relational Databases Avoid Multivalued Dependencies by Breaking Data Into Multiple Tables How to Create Database Relationships in Access Transitive Dependencies Can Creep Into Your Data and Muck with Its Accuracy Ditch Your Spreadsheet for a Database to Access the Power of Your Data An Easy Guide to Creating Databases and Tables in SQL The Role of Referential Integrity in Your Database Primary Keys in a Database and What Makes a Good Key Here's How to Create Foreign Keys in Microsoft SQL Server Protect Your Data by Normalizing It to at Least 2NF An Intro to Databases That's Suitable for the Brand New Beginner What Are Schemas and What Is Their Relationship to Databases?