Working with Multiple Tables

Most databases contain multiple tables

• This is a direct result of normalization

Use keys to determine relationships between rows in different tables

• A primary key identifies a unique row in a table
• A foreign key references a row in another table

Create foreign key constraints to enforce referential integrity

• This prevents invalid data insertions
• It can be used to prevent deletions or updates that will “orphan” rows

The procedure while working with multiple tables

• Use the CREATE TABLE statement to create tables
• Use the INSERT statement to add rows to a table
• Use the SELECT statement to retrieve rows from a table
• Use constraints that define relationships between primary keys and foreign keys to enforce referential integrity