MySQL in a Nutshell, 2nd Edition

Appendix B. Operators

Operators are used in mathematical or logical operations. An operator is typically placed between two values (i.e., numbers, strings, columns, or expressions) that you want to compare or evaluate. There are four types of operators: arithmetic, relational, logical, and bitwise. This appendix provides a listing of operators grouped into these four types. This appendix also includes a list of special pattern-matching characters and constructs for regular expressions.

Arithmetic Operators

The arithmetic operators in MySQL work only on numbers, not on strings. However, MySQL will convert a string into a number when in a numeric context if it can. If it can’t convert a particular string, it will return 0. Table B-1 lists the arithmetic operators allowed.

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 rather truncates them.

Table B-1. Arithmetic operators

Operator	Use
+	Addition
–	Subtraction and negation
*	Multiplication
/	Division
DIV	Division of integers
%	Modulo division