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Common Mistakes when Creating a Database

Deletion of Fields: this can happen when someone has direct access to the database and deletes or edits fields by accident. To prevent this from happening the database should be updated and backed up on a regular basis. If the database is updated regularly there should not be a problem with deletion of files. Another way that you can prevent this from happening is to only allow members of staff use a (read only) copy of the data base, this way nothing can be moved around Validation rules:

Validation rules that are put into the database in the creation. They stop bad data being saved in your table.  You can create a rule for a field , or for the table. Use the table's rule to compare fields.

Null Values:   NULL values indicates that the field 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.

Incorrect data types: when completing a data entry form there are certain fields in which you can write. These are called input masks the masks can be made to only accept data such as integers, floating point numbers, characters, strings and arrays.