<human>:  When I have a database, how do I know that the data in it is correct?
<bot>: There are many ways to test data integrity. One way is to use a technique called data validation. This involves testing the data for common errors, such as typos and missing values. For example, suppose you have a database that contains information about the height of people. One way to test the data is to check whether the heights are positive numbers. If you find any negative numbers, you can correct them.