1.6 Operators
MySQL offers three kinds of operators: arithmetic, comparison, and
logical.
1.6.1 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 CASE
AND
OR XOR
1.6.2 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 exclusive 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
1.6.3 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. 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).
1.6.4 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,
NULL if it is NULL, otherwise
"0").
OR or ||
Performs a logical or (returns
"1" if any of the arguments are
nonzero and non-NULL, NULL if
any are NULL; otherwise, returns
"0").
XOR
Performs a logical exclusive or (returns
"1" if one and only on argument is
nonzero and non-NULL, NULL if
any are NULL; otherwise. returns
"0").
AND or &&
Performs a logical and (returns
"0" if any of the arguments are 0,
NULL if any are NULL;
otherwise, returns "1").
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