1. Insertion Anomaly: This occurs when certain attributes cannot be inserted into the database without the presence of other attributes. For example, in a student database, if all tables are not properly structured, you might be forced to know the Course information before you can enter Student information, which isn’t practical as a Student can exist without being enrolled in any course.
  2. Deletion Anomaly: This occurs when deletion of certain data inadvertently leads to other data getting deleted. For instance, if a student who is the only one enrolled in a certain course drops out, and if student data and course data are stored in the same table, deleting that student’s record might also remove valuable information about the course itself.
  3. Update Anomaly: This happens when a change in some piece of data necessitates changes to other data to maintain consistency. For example, if a teacher’s address is stored in multiple records (for different subjects that teacher teaches), updating the teacher’s address would require modifying all these records. Failure to do so can result in inconsistent data.