Functions
Functions
and operators can be used in SQL statements. This section lists these
functions and operators and provides examples. A full list of
functions with examples is available in Section 7.4 of the
manual.html
file distributed with MySQL.
Arithmetic and comparison operators
Table 3-2 shows examples of the basic
arithmetic and
comparison operators in
SELECT
statements. The basic arithmetic operators
are *
, +
, /
,
and -
, as well as the parentheses ( )
to control the order of evaluation of an expression.
Table 3-2. Using the arithmetic and comparison operators
Statement |
Output |
---|---|
SELECT 8+3*2; |
14 |
SELECT (8+3)*2; |
22 |
SELECT 2=2; |
1 |
SELECT 1!=2; |
1 |
SELECT 2<=2; |
1 |
SELECT 3<=2; |
0 |
The comparison operators include =
,
!=
, <
,
>
, <=
, and
>=
. Four examples are shown in Table 3-2. If an expression evaluates as
true
, the output is 1; if an expression evaluates
as false
, the output is 0. To test for equality, a
single equals sign is used; this contrasts with PHP, where the double
equals (==)
is used for equality tests, and a
single equals sign is used for assignment.
To test whether two items are equal, the !=
operator is provided. Less-than-or-equal-to is represented by
<=
, and greater-than-or-equal-to is represented
by >=
. Parentheses can explicitly express the
evaluation order.
String-comparison operators and functions
Table 3-3 shows examples of the MySQL string-comparison operators and functions. Many of the MySQL string functions shown here are similar to PHP functions, ...
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