SQL has three logical operators, shown in order of precedence:

Use parentheses to change the order of evaluation. For example, the following expression:

is evaluated as:

When parentheses are used as follows:

the DBMS Server evaluates (exprA OR exprB) first, then uses the AND operator for the result with exprC.

Parentheses can also be used to change the default evaluation order of a series of expressions combined with the same logical operator. For example, the following expression:

is evaluated as:

To change this default left-to-right grouping, use parentheses as follows:

The parentheses direct the DBMS Server to use the AND operator for exprB and exprC, then use the AND operator for that result with exprA.