Educator

Linking Tables

• Database normalization is a process that involves structuring a relational database to help reduce common problems involving:
  • Difficulties in searching data
  • Having large numbers of empty fields
  • Needing to re-structure tables frequently
  • Redundant storage of the same data
• A foreign key is a column in one table whose value represents a primary key of another table.
• A linking table contains two or more foreign key values in each row that serve to link one row of one table with one row of another table.
• Tables can use more than one column to comprise its primary key. Such a table is defined using the following syntax:

  CREATE TABLE depts_items (
  

  deptID INT UNSIGNED,
  itemID INT UNSIGNED,
  PRIMARY KEY (deptID, itemID)

  );