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.
The spots have yet to be identified by a microbiologist. Some of the paintings are in critical condition and color tones are fading. The cave, in addition, is currently very wet and water can be seen running over the face of paintings. The limestone which gave the cave a remarkable brilliance, has turned gray. Current managers have found no treatment and the spots continue to spread.