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SQL Anywhere 11.0.0 » SQL Anywhere Server - SQL Usage » Designing and Creating Databases » Ensuring data integrity » Introduction to data integrity


How data can become invalid

Here are a few examples of how the data in a database may become invalid if proper checks are not made. You can prevent each of these examples from occurring using facilities described in this chapter.

Incorrect information
  • An operator types the date of a sales transaction incorrectly.
  • An employee's salary becomes ten times too small because the operator missed a digit.
Duplicated data
  • Two different people add the same new department (with DepartmentID 200) to the Departments table of the organization's database.
Foreign key relations invalidated
  • The department identified by DepartmentID 300 closes down and one employee record inadvertently remains unassigned to a new department.