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.
Black hairy or furry tongue or yellow furry tongue: This is caused by dead skin and food buildup, and occurs commonly when the papillae become enlarged, swollen, or rough. When this buildup is paired with bacteria or yeast, it can cause the tongue to look yellow or black and hairy.