You can use group parentheses to group a set of expressions. A group is a set of expressions that are explicitly combined with parentheses. You can only group a set of expressions that form a subclause, which is a set of expressions that can be logically treated as a single expression.
Use group parentheses to make complex expressions easier to understand or to force a certain order of evaluation. For example, when more than one OR expression occurs within a complex query, use parentheses to indicate which expression should be evaluated first.
By making a set of expressions a group, you ensure that the expressions of the group are treated together and evaluated first. Groups have a higher operator precedence than the logical operators AND, OR, and NOT. For more information about how queries are evaluated and operator precedence, see About Logical Operators and Operator Precedence.