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Chapter 17. Operators and Functions
Like any other programming language, SQL carries among its core elements operators and named procedures. This reference lists all those operators and functions and explains how they evaluate into useful expressions.
17.1. Operators
MySQL offers three kinds of operators: arithmetic, comparison, and logical.
17.1.1. Rules of Precedence
When your SQL contains complex expressions, the subexpressions are evaluated based on MySQL's rules of precedence. Of course, you may always override MySQL's rules of precedence by enclosing an expression in parentheses.
-
BINARY
-
NOT
-
- (unary minus)
-
* / %
-
+ -
-
<< >>
-
&
-
|
-
< <= > >= = <=> <> IN IS LIKE REGEXP
-
BETWEEN
-
AND
-
OR
17.1.2. Arithmetic Operators
Arithmetic operators perform basic arithmetic on two values.
- +
- Adds two numerical values
- -
- Subtracts two numerical values
- *
- Multiplies two numerical values
- /
- Divides two numerical values
- %
- Gives the modulo of two numerical values
- |
- Performs a bitwise OR on two integer values
- &
- Performs a bitwise AND on two integer values
- <<
- Performs a bitwise left shift on an integer value
- >>
- Performs a bitwise right shift on an integer value
17.1.3. Comparison Operators
Comparison operators compare values and return 1 if the comparison is true and 0 otherwise. Except for the <==> operator, NULL values cause a comparison operator to evaluate to NULL.
- <> or !=
- Match rows if the two values are not equal.
- <=
- Match rows if the left value is less than or equal to the right value.
- <
- Match rows if the left value is less than the right value.
- >=
- Match rows if the left value is greater than or equal to the right value.
- >
- Match rows if the left value is greater than the right value.
- value BETWEEN value1 AND value2
- Match rows if value is between value1 and value2, or equal to one of them.
- value IN (value1,value2,...)
- Match rows if value is among the values listed.
- value NOT IN (value1, value2,...)
- Match rows if value is not among the values listed.
- value1 LIKE value2
- Compares value1 to value2 and matches the rows if they match. The righthand value can contain the wildcard '%', which matches any number of characters (including 0), and '_', which matches exactly one character. This is probably the single most used comparison in SQL. Its most common use is comparing a field value with a literal containing a wildcard (e.g., SELECT name FROM people WHERE name LIKE 'B%').
- value1 NOT LIKE value2
- Compares value1 to value2 and matches the rows if they differ. This is identical to NOT (value1 LIKE value2).
- value1 REGEXP/RLIKE value2
- Compares value1 to value2 using the extended regular expression syntax and matches the rows if the two values match. The righthand value can contain full Unix regular expression wildcards and constructs (e.g., SELECT name FROM people WHERE name RLIKE '^B.*').
- value1 NOT REGEXP value2
- Compares value1 to value2 using the extended regular expression syntax and matches the rows if they differ. This is identical to NOT (value1 REXEXP value2).
17.1.4. Logical Operators
Logical operators check the truth value of one or more expressions. In SQL terms, a logical operator checks whether its operands are 0, nonzero, or NULL. A 0 value means false, nonzero means true, and NULL means no value.
- NOT or !
- Performs a logical not (returns 1 if the value is 0 or NULL; otherwise, returns 0)
- OR or ||
- Performs a logical or (returns 1 if any of the arguments are nonzero and non-NULL; otherwise, returns 0)
- AND or &&
- Performs a logical and (returns 0 if any of the arguments are 0 or NULL; otherwise, returns 1)
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| 16.4. Complex Data Types |  | 17.2. Functions |
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