Defining Table Constraints and Indexes

This section contains the following topics.

• About Constraints
  You can define Constraints to enforce limitations on data in each row of a table.
• Check Constraint
  The check Constraint allows you to specify allowable values for a particular Column.
• Non-Unique Index
  You can define a non-unique index on any Column or set of Columns.
• Primary Key
  A Primary Key is a Column or set of Columns whose value(s) identify a row in a table as unique.
• Unique Key
  A Unique Key is similar to a Primary Key in that it can include one or more Columns whose value(s) identify a row as unique.