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.
Hantavirus pulmonary syndrome is a disease that can cause blood spots under the skin, says Mayo Clinic. The first symptoms resemble the flu, then more serious symptoms appear, including fluid on the lungs and dangerously low blood pressure. Endocarditis is an infection that strikes the valves or inner lining of the heart, according to WebMD.