<left logical expression> AND <right logical expression> evaluates to true,
when the left and the right hand side logical expressions are true.
Evaluates to false otherwise.
Parentheses may be used to simply make the complete logical expression more readable, but can also be used to change the meaning of the complete logical expression. This is possible through the order of precedence for logical expressions, described in the Functions and Operators section.
If one of the input expressions is NULL, than the result will be false since it could not fulfill the logical AND.