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.
Koplik spots (small bluish yellow spots) occur in the mouth on buccal mucosa. The maculopapular rash appears first on the head, and then progressively spreads over the chest, trunk, and then limbs, eventually covering the entire body. Infection of the measles virus occurs through the respiratory tract. The receptor for the measles virus is the human complement regulatory cofactor protein CD46.