Unit 18 D1 Database Errors Updated

Whenever data is entered into a database, somewhere along the line someone is bound to make an error. This happens when someone enters data incorrectly and the database cannot register it correctly for example putting in invalid ages or entering ridiculous amounts of money into a cash system. 

Multiple choice and drop down options gives the user of the database multiple options to select , instead of putting in an answer that might not register with the database.Also rules can be set in place that can stop a user entering incorrect values to the database such as character limit checks or presence checks, these are known as validation rules , these keep the databases clean and full of safe data. Input masks are also a validation rule , they prevent users also entering false data by only allowing either numerical or alphabetical characters to be inputted. For example someone could be entering a credit card number and accidently put in a letter instead of a number , these masks prevent the users from submitting data like this to the database also. 

Renaming can also be an issue too when it comes to databases. Someone could rename a piece of data incorrectly which could cause the database to either not function or register false data.  However this can be avoided if admins are only allowed to access the database and change data or if limits are put in place that prevents  users to change fields of data or the names. 

Also a person can accidently delete large or small amounts of fields. This can be avoided however if the database is checked twice or more, enter data correctly or back ups are made of the database itself or that admins can only access the database.

NULL indicates that the value is unknown. A value of NULL is different from an empty or zero value. No two null values are equal. Comparisons between two null values, or between a NULL and any other value, return unknown because the value of each NULL is unknown. This can be avoided if validation fields are put in to prevent people from entering no values.