PostgreSQL 8.1.23 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 between 0.0 and 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 | 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, an upper bound of b1, and a lower bound of 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.
The modulo operator returns a negative result with negative numbers. This is the same as C and Java, but different from Perl and Python.
The width_bucket function is sensitive to argument types - for example width_bucket(float8, numeric,numeric,numeric) results in function not found. But if you explicitly cast all arguments to numeric it works fine
The subtraction operator (-) treats nulls differently than zeros. For instance the following will return null instead of 3:
SELECT SUM(debits) - SUM(credits) as balance FROM entries WHERE accno='2500'
entries
id | accno | debits | credits
-----------------------------------
1 | 2500 | 3 |
If you need to use operators on tables that might have null values you can use the COALESCE function:
SELECT COALESCE(field1, 0) + COALESCE(field2, 0) FROM tablename;