Unary operator operates on one operand, binary operator operates on two.
The two general classes of operators are unary and binary.
A unary operator typically appears with its operand in this format:
operator operand
A binary operator appears with its operands in this format:
operand1 operator operand2
If an operator is given a NULL operand, the result is always NULL, with the following exceptions:
AND OR XOR
See Null Values in Expressions for rules on using NULLs with the AND, XOR, and OR operators.