PostgreSQL 8.2.23 Documentation | ||||
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Mathematical operators are provided for many PostgreSQL types. For types without common mathematical conventions for all possible permutations (e.g., date/time types) we describe the actual behavior in subsequent sections.
Table 9-2 shows the available mathematical operators.
Table 9-2. Mathematical Operators
Operator | Description | Example | Result |
---|---|---|---|
+ | addition | 2 + 3 | 5 |
- | subtraction | 2 - 3 | -1 |
* | multiplication | 2 * 3 | 6 |
/ | division (integer division truncates results) | 4 / 2 | 2 |
% | modulo (remainder) | 5 % 4 | 1 |
^ | exponentiation | 2.0 ^ 3.0 | 8 |
|/ | square root | |/ 25.0 | 5 |
||/ | cube root | ||/ 27.0 | 3 |
! | factorial | 5 ! | 120 |
!! | factorial (prefix operator) | !! 5 | 120 |
@ | absolute value | @ -5.0 | 5 |
& | bitwise AND | 91 & 15 | 11 |
| | bitwise OR | 32 | 3 | 35 |
# | bitwise XOR | 17 # 5 | 20 |
~ | bitwise NOT | ~1 | -2 |
<< | bitwise shift left | 1 << 4 | 16 |
>> | bitwise shift right | 8 >> 2 | 2 |
The bitwise operators work only on integral data types, whereas the others are available for all numeric data types. The bitwise operators are also available for the bit string types bit and bit varying, as shown in Table 9-10.
Table 9-3 shows the available mathematical functions. In the table, dp indicates double precision. Many of these functions are provided in multiple forms with different argument types. Except where noted, any given form of a function returns the same data type as its argument. The functions working with double precision data are mostly implemented on top of the host system's C library; accuracy and behavior in boundary cases may therefore vary depending on the host system.
Table 9-3. Mathematical Functions
Function | Return Type | Description | Example | Result |
---|---|---|---|---|
abs (x) |
(same as x) | absolute value | abs(-17.4) | 17.4 |
cbrt (dp) |
dp | cube root | cbrt(27.0) | 3 |
ceil (dp or
numeric) |
(same as input) | smallest integer not less than argument | ceil(-42.8) | -42 |
ceiling (dp or
numeric) |
(same as input) | smallest integer not less than argument (alias for
ceil ) |
ceiling(-95.3) | -95 |
degrees (dp) |
dp | radians to degrees | degrees(0.5) | 28.6478897565412 |
exp (dp or
numeric) |
(same as input) | exponential | exp(1.0) | 2.71828182845905 |
floor (dp or
numeric) |
(same as input) | largest integer not greater than argument | floor(-42.8) | -43 |
ln (dp or
numeric) |
(same as input) | natural logarithm | ln(2.0) | 0.693147180559945 |
log (dp or
numeric) |
(same as input) | base 10 logarithm | log(100.0) | 2 |
log (b
numeric, x numeric) |
numeric | logarithm to base b | log(2.0, 64.0) | 6.0000000000 |
mod (y,
x) |
(same as argument types) | remainder of y/x | mod(9,4) | 1 |
pi () |
dp | "π" constant | pi() | 3.14159265358979 |
power (a
dp, b
dp) |
dp | a raised to the power of b | power(9.0, 3.0) | 729 |
power (a
numeric, b numeric) |
numeric | a raised to the power of b | power(9.0, 3.0) | 729 |
radians (dp) |
dp | degrees to radians | radians(45.0) | 0.785398163397448 |
random () |
dp | random value in the range 0.0 <= x < 1.0 | random() | |
round (dp or
numeric) |
(same as input) | round to nearest integer | round(42.4) | 42 |
round (v
numeric, s int) |
numeric | round to s decimal places | round(42.4382, 2) | 42.44 |
setseed (dp) |
int | set seed for subsequent random() calls (value between 0 and 1.0) | setseed(0.54823) | 1177314959 |
sign (dp or
numeric) |
(same as input) | sign of the argument (-1, 0, +1) | sign(-8.4) | -1 |
sqrt (dp or
numeric) |
(same as input) | square root | sqrt(2.0) | 1.4142135623731 |
trunc (dp or
numeric) |
(same as input) | truncate toward zero | trunc(42.8) | 42 |
trunc (v
numeric, s int) |
numeric | truncate to s decimal places | trunc(42.4382, 2) | 42.43 |
width_bucket (op numeric,
b1 numeric, b2
numeric, count int) |
int | return the bucket to which operand would be assigned in an equidepth histogram with count buckets, in the range b1 to b2 | width_bucket(5.35, 0.024, 10.06, 5) | 3 |
Finally, Table 9-4 shows the available trigonometric functions. All trigonometric functions take arguments and return values of type double precision.
For the trig functions, noting that they accept radians (as opposed to degrees) as their arguments may be helpful to newer developers.
function to work out the scale of a numeric value.
(Scale is the number of digits afer the deciaml point)
CREATE OR REPLACE FUNCTION scale(x numeric)
RETURNS text AS
$BODY$
DECLARE
res int;
BEGIN
IF (x - x::int)=0 THEN
-- catch integers
res = 0;
ELSE
res = length(x - floor(x)::int) - 2;
END IF;
RETURN res;
END;
$BODY$
LANGUAGE 'plpgsql' VOLATILE;