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9.3. Mathematical Functions and Operators
Mathematical operators are provided for manyPostgreSQL 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 typesbit andbit varying, as shown inTable 9-11.
Table 9-3 shows the available mathematical functions. In the table,dp indicatesdouble 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 withdouble 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 ornumeric) | (same as input) | smallest integer not less than argument | ceil(-42.8) | -42 |
ceiling(dp ornumeric) | (same as input) | smallest integer not less than argument (alias forceil) | ceiling(-95.3) | -95 |
degrees(dp) | dp | radians to degrees | degrees(0.5) | 28.6478897565412 |
div(ynumeric,xnumeric) | numeric | integer quotient ofy/x | div(9,4) | 2 |
exp(dp ornumeric) | (same as input) | exponential | exp(1.0) | 2.71828182845905 |
floor(dp ornumeric) | (same as input) | largest integer not greater than argument | floor(-42.8) | -43 |
ln(dp ornumeric) | (same as input) | natural logarithm | ln(2.0) | 0.693147180559945 |
log(dp ornumeric) | (same as input) | base 10 logarithm | log(100.0) | 2 |
log(bnumeric,xnumeric) | numeric | logarithm to baseb | log(2.0, 64.0) | 6.0000000000 |
mod(y,x) | (same as argument types) | remainder ofy/x | mod(9,4) | 1 |
pi() | dp | "π" constant | pi() | 3.14159265358979 |
power(adp,bdp) | dp | a raised to the power ofb | power(9.0, 3.0) | 729 |
power(anumeric,bnumeric) | numeric | a raised to the power ofb | power(9.0, 3.0) | 729 |
radians(dp) | dp | degrees to radians | radians(45.0) | 0.785398163397448 |
round(dp ornumeric) | (same as input) | round to nearest integer | round(42.4) | 42 |
round(vnumeric,sint) | numeric | round tos decimal places | round(42.4382, 2) | 42.44 |
sign(dp ornumeric) | (same as input) | sign of the argument (-1, 0, +1) | sign(-8.4) | -1 |
sqrt(dp ornumeric) | (same as input) | square root | sqrt(2.0) | 1.4142135623731 |
trunc(dp ornumeric) | (same as input) | truncate toward zero | trunc(42.8) | 42 |
trunc(vnumeric,sint) | numeric | truncate tos decimal places | trunc(42.4382, 2) | 42.43 |
width_bucket(opnumeric,b1numeric,b2numeric,countint) | int | return the bucket to whichoperand would be assigned in an equidepth histogram withcount buckets, in the rangeb1 tob2 | width_bucket(5.35, 0.024, 10.06, 5) | 3 |
width_bucket(opdp,b1dp,b2dp,countint) | int | return the bucket to whichoperand would be assigned in an equidepth histogram withcount buckets, in the rangeb1 tob2 | 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 subsequentrandom() calls (value between -1.0 and 1.0, inclusive) |
The characteristics of the values returned byrandom() depend on the system implementation. It is not suitable for cryptographic applications; seepgcrypto module for an alternative.
Finally,Table 9-5 shows the available trigonometric functions. All trigonometric functions take arguments and return values of typedouble precision. Trigonometric functions arguments are expressed in radians. Inverse functions return values are expressed in radians. See unit transformation functionsradians() anddegrees() above.