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.
Age spots are blotches of darker skin color that are common on the face and hands. While anyone can develop these spots from spending too much time in the sun, research suggests smokers are more susceptible. In this image, the twin on the right spent decades smoking and sunbathing, while her sister did not.