Arithmetic and bitwise operators are handled before logical operators. When more than one logical operator is used in a statement, not is evaluated first, then and, and finally or. See “Bitwise operators”.
For example, the following query finds all the business books in the titles table, no matter what their advances are, as well as all psychology books that have an advance of more than 5500. The advance condition pertains only to psychology books because the and is handled before the or.
select title_id, type, advance from titles where type = "business" or type = "psychology" and advance > 5500
title_id type advance -------- ---------- ---------- BU1032 business 5,000.00 BU1111 business 5,000.00 BU2075 business 10,125.00 BU7832 business 5,000.00 PS1372 psychology 7,000.00 PS2106 psychology 6,000.00 (6 rows affected)
You can change the meaning of the query by adding parentheses to force evaluation of the or first. This query finds all business and psychology books with advances of more than 5500:
select title_id, type, advance from titles where (type = "business" or type = "psychology") and advance > 5500
title_id type advance -------- ---------- --------- BU2075 business 10,125.00 PS1372 psychology 7,000.00 PS2106 psychology 6,000.00 (3 rows affected)
