Mathematical Functions and Operators
6.3. Mathematical Functions and Operators
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 6-2 shows the available mathematical operators.
Table 6-2. Mathematical Operators
| Name | 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 |
| & | binary AND | 91 & 15 | 11 |
| | | binary OR | 32 | 3 | 35 |
| # | binary XOR | 17 # 5 | 20 |
| ~ | binary NOT | ~1 | -2 |
| << | binary shift left | 1 << 4 | 16 |
| >> | binary shift right | 8 >> 2 | 2 |
The "binary" operators are also available for the bit string types BIT and BIT VARYING, as shown in Table 6-3. Bit string arguments to &, |, and # must be of equal length. When bit shifting, the original length of the string is preserved, as shown in the table.
Table 6-3. Bit String Binary Operators
| Example | Result |
|---|---|
| B'10001' & B'01101' | 00001 |
| B'10001' | B'01101' | 11101 |
| B'10001' # B'01101' | 11110 |
| ~ B'10001' | 01110 |
| B'10001' << 3 | 01000 |
| B'10001' >> 2 | 00100 |
Table 6-4 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 datatype 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 6-4. 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 |
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 | "Pi" constant | pi() | 3.14159265358979 |
pow(x dp,
e dp) | dp | raise a number to exponent e | pow(9.0, 3.0) | 729 |
pow(x numeric,
e numeric) | numeric | raise a number to exponent e | pow(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 integer) | 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 integer) | numeric | truncate to s decimal places | trunc(42.4382, 2) | 42.43 |
Finally, Table 6-5 shows the available trigonometric functions. All trigonometric functions take arguments and return values of type double precision.