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.
Some other causes of coated white tongue are accumulation of keratin or dead skin cells on the surface of tongue, tobacco abuse, consumption of extremely hot foods or beverages etc. Abnormal buildup of keratin is generally caused by dehydration as it tends to dry out saliva, thereby making the tongue dry.