9.3. Mathematical Functions and Operators
Mathematical operators are provided for many PostgreSQL types. For types without standard mathematical conventions (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 the result) | 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 9-11.
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 can therefore vary depending on the host system.
Table 9-3. Mathematical Functions
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
abs(x) |
(same as input) | 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 |
div(y numeric, x
numeric) |
numeric | integer quotient of y/x | div(9,4) | 2 |
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 |
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 |
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 |
width_bucket(op
dp, b1
dp, b2
dp, 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 |
Table 9-4 shows functions for generating random numbers.
Table 9-4. Random Functions
| Function | Return Type | Description |
|---|---|---|
random() |
dp | random value in the range 0.0 <= x < 1.0 |
setseed(dp) |
void | set seed for subsequent random() calls (value between -1.0 and 1.0, inclusive) |
The characteristics of the values returned by random() depend on
the system implementation. It is not suitable for cryptographic
applications; see pgcrypto module for
an alternative.
Finally, Table 9-5
shows the available trigonometric functions. All trigonometric
functions take arguments and return values of type double precision. Trigonometric functions arguments
are expressed in radians. Inverse functions return values are
expressed in radians. See unit transformation functions
radians()
and degrees() above.