The SQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank. A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces.
Someone with red spots on their tongue may be suffering from geographic tongue, according to Mayo Clinic. Other causes of red spots on the tongue include folic acid and vitamin B-12 deficiencies and scarlet fever, WebMD states. Continue Reading.
Tongue injuries (piercings and dental appliances) are a possible cause of black patches on your tongue especially if the injury cause sores. You can also end up with dark spots on tongue from biting or after biting your tongue. Anemia. Anemia is another possible cause of black tongue spots. Many people have reported this problem.