What is the ?: (question mark and colon operator aka. conditional or "ternary") operator and how can I use it?
Note that the result of the % operator is equal to x – (x / y) * y and that if y is zero, a DivideByZeroException is thrown. If x and y are non-integer values x % y is computed as x – n * y, where n is the largest possible integer that is less than or equal to x / y (more details in the C# 4.0 Specification in section 7.8.3 Remainder operator).
30 <> operator means not equal to in MS SQL. It compares two expressions (a comparison operator). When you compare nonnull expressions, the result is TRUE if the left operand is not equal to the right operand; otherwise, the result is FALSE. If either or both operands are NULL, see the topic SET ANSI_NULLS (Transact-SQL). See here : Not Equal To
17 I suspect this is a leftover from C++ where people override the ! operator, but not the bool operator. So to get a negative (or positive) answer in that case, you would first need to use the ! operator to get a Boolean, but if you wanted to check the positive case you would use !!.
What does the !! (double exclamation mark) operator do in JavaScript ...
The & operator does "run these 3 functions, and if one of them returns false, execute the else block", while the | does "only run the else block if none return false" - can be useful, but as said, often it's a design smell. There is a Second use of the | and & operator though: Bitwise Operations.