The SQL NULL is the term used to represent a missing value. A NULL value in a table is a value in a field that appears to be blank. A field with a NULL value is a field with no value. It is very important to understand that a NULL value is different than a zero value or a field that contains spaces.
Median rhomboid glossitis is a condition that can affect your tongue if you have oral thrush. It causes a red, smooth patch or lump to develop in the middle of the top part of your tongue, which can be sore. You're more likely to develop oral thrush if you: have recently taken antibiotics.
Black hairy or furry tongue or yellow furry tongue: This is caused by dead skin and food buildup, and occurs commonly when the papillae become enlarged, swollen, or rough. When this buildup is paired with bacteria or yeast, it can cause the tongue to look yellow or black and hairy.