Primary and foreign keys

Professional databases follow consistent patterns for connecting tables. Learning these patterns helps you identify join columns quickly. Databases use a pattern called primary key / foreign key (PK/FK) to organize relationships between tables. Understanding this pattern helps you know which columns to join on. Primary Key A primary key uniquely identifies each row in a table. No two rows can have the same primary key value. Common examples: Foreign Key A foreign key is a column that references the primary key of another table. It creates the link between tables: When you join tables, you typically connect a foreign key to its referenced primary key. This pattern appears in 70-80% of joins in real databases. The primary key and foreign key pattern is so universal in relational databases th