The arithmetic operators in MySQL work only on numbers, and not on strings. However, MySQL will convert a string as a number when in a numeric context if it can. If it can't convert a particular string, it will convert it to 0. The arithmetic operators allowed are listed in Table B-1.
The minus sign may be used for subtracting numbers or for setting a number to a negative. The DIV operator converts values to integers and returns only integers. It doesn't round fractions that would be returned, but truncates them. |