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.
Yellow tongue usually occurs when the papillae (tiny projections) on the surface of your tongue become enlarged and yellow-colored from bacteria growing in your mouth. Rarely, yellow tongue may be a sign of jaundice, a yellowing of your eyes and skin that might indicate liver or gallbladder problems.