A value of NULL indicates that the value 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.
Skin Spots on the Face. Most causes of spots on face are harmless. They can be a variety of colors including white, red, black or brown. Common causes include cumulative sun exposure, acne, and skin tags. Keratoacanthoma (hyperkeratosis) is a lesion that grows rapidly, usually on areas exposed to the sun.
An Overview of Rubella Transmission. Rubella (also known as German measles or three-day measles) is a contagious illness spread by coughing and sneezing. A person with rubella can transmit the virus anytime from about seven days prior to the onset of the rash to seven days after the onset.Even if rubella symptoms never develop, a person can spread rubella if he or she becomes infected with rubella virus.ollowing rubella transmission, a person does not immediately become sick. Once the rubella virus enters the body, it travels to the nose and back of the throat, where it begins to multiply. It can also travel to other parts of the body through the bloodstream and lymph system.