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 9.4 shows the mathematical operators that are available for the standard numeric types. Unless otherwise noted, operators shown as accepting numeric_type are available for all the types smallint, integer, bigint, numeric, real, and double precision. Operators shown as accepting integral_type are available for the types smallint, integer, and bigint. Except where noted, each form of an operator returns the same data type as its argument(s). Calls involving multiple argument data types, such as integer + numeric, are resolved by using the type appearing later in these lists.

Table 9.4. Mathematical Operators

Operator Description Example(s)
numeric_type + numeric_type → *numeric_type* Addition 2 + 3 → 5
+ numeric_type → *numeric_type* Unary plus (no operation) + 3.5 → 3.5
numeric_type - numeric_type → *numeric_type* Subtraction 2 - 3 → -1
- numeric_type → *numeric_type* Negation - (-4) → 4
numeric_type * numeric_type → *numeric_type* Multiplication 2 * 3 → 6
numeric_type / numeric_type → *numeric_type* Division (for integral types, division truncates the result towards zero) 5.0 / 2 → 2.5000000000000000 5 / 2 → 2 (-5) / 2 → -2
numeric_type % numeric_type → *numeric_type* Modulo (remainder); available for smallint, integer, bigint, and numeric 5 % 4 → 1
numeric ^ numeric → numeric double precision ^ double precision → double precision Exponentiation 2 ^ 3 → 8 Unlike typical mathematical practice, multiple uses of ^ will associate left to right by default: 2 ^ 3 ^ 3 → 512 2 ^ (3 ^ 3) → 134217728
|/ double precision → double precision Square root |/ 25.0 → 5
||/ double precision → double precision Cube root ||/ 64.0 → 4
@ numeric_type → *numeric_type* Absolute value @ -5.0 → 5
integral_type & integral_type → *integral_type* Bitwise AND 91 & 15 → 11
integral_type | integral_type → *integral_type* Bitwise OR 32 | 3 → 35
integral_type # integral_type → *integral_type* Bitwise exclusive OR 17 # 5 → 20
~ integral_type → *integral_type* Bitwise NOT ~1 → -2
integral_type << integer → *integral_type* Bitwise shift left 1 << 4 → 16
integral_type >> integer → *integral_type* Bitwise shift right 8 >> 2 → 2

Table 9.5 shows the available mathematical functions. 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(s); cross-type cases are resolved in the same way as explained above for operators. 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 9.5. Mathematical Functions

Function Description Example(s)
abs ( numeric_type ) → *numeric_type* Absolute value abs(-17.4) → 17.4
cbrt ( double precision ) → double precision Cube root cbrt(64.0) → 4
ceil ( numeric ) → numeric ceil ( double precision ) → double precision Nearest integer greater than or equal to argument ceil(42.2) → 43 ceil(-42.8) → -42
ceiling ( numeric ) → numeric ceiling ( double precision ) → double precision Nearest integer greater than or equal to argument (same as ceil) ceiling(95.3) → 96
degrees ( double precision ) → double precision Converts radians to degrees degrees(0.5) → 28.64788975654116
div ( y numeric, x numeric ) → numeric Integer quotient of y/x (truncates towards zero) div(9, 4) → 2
exp ( numeric ) → numeric exp ( double precision ) → double precision Exponential (e raised to the given power) exp(1.0) → 2.7182818284590452
factorial ( bigint ) → numeric Factorial factorial(5) → 120
floor ( numeric ) → numeric floor ( double precision ) → double precision Nearest integer less than or equal to argument floor(42.8) → 42 floor(-42.8) → -43
gcd ( numeric_type, numeric_type ) → *numeric_type* Greatest common divisor (the largest positive number that divides both inputs with no remainder); returns 0 if both inputs are zero; available for integer, bigint, and numeric gcd(1071, 462) → 21
lcm ( numeric_type, numeric_type ) → *numeric_type* Least common multiple (the smallest strictly positive number that is an integral multiple of both inputs); returns 0 if either input is zero; available for integer, bigint, and numeric lcm(1071, 462) → 23562
ln ( numeric ) → numeric ln ( double precision ) → double precision Natural logarithm ln(2.0) → 0.6931471805599453
log ( numeric ) → numeric log ( double precision ) → double precision Base 10 logarithm log(100) → 2
log10 ( numeric ) → numeric log10 ( double precision ) → double precision Base 10 logarithm (same as log) log10(1000) → 3
log ( b numeric, x numeric ) → numeric Logarithm of x to base b log(2.0, 64.0) → 6.0000000000
min_scale ( numeric ) → integer Minimum scale (number of fractional decimal digits) needed to represent the supplied value precisely min_scale(8.4100) → 2
mod ( y numeric_type, x numeric_type ) → *numeric_type* Remainder of y/x; available for smallint, integer, bigint, and numeric mod(9, 4) → 1
pi ( ) → double precision Approximate value of π pi() → 3.141592653589793
power ( a numeric, b numeric ) → numeric power ( a double precision, b double precision ) → double precision a raised to the power of b power(9, 3) → 729
radians ( double precision ) → double precision Converts degrees to radians radians(45.0) → 0.7853981633974483
round ( numeric ) → numeric round ( double precision ) → double precision Rounds to nearest integer. For numeric, ties are broken by rounding away from zero. For double precision, the tie-breaking behavior is platform dependent, but “round to nearest even” is the most common rule. round(42.4) → 42
round ( v numeric, s integer ) → numeric Rounds v to s decimal places. Ties are broken by rounding away from zero. round(42.4382, 2) → 42.44
scale ( numeric ) → integer Scale of the argument (the number of decimal digits in the fractional part) scale(8.4100) → 4
sign ( numeric ) → numeric sign ( double precision ) → double precision Sign of the argument (-1, 0, or +1) sign(-8.4) → -1
sqrt ( numeric ) → numeric sqrt ( double precision ) → double precision Square root sqrt(2) → 1.4142135623730951
trim_scale ( numeric ) → numeric Reduces the value's scale (number of fractional decimal digits) by removing trailing zeroes trim_scale(8.4100) → 8.41
trunc ( numeric ) → numeric trunc ( double precision ) → double precision Truncates to integer (towards zero) trunc(42.8) → 42 trunc(-42.8) → -42
trunc ( v numeric, s integer ) → numeric Truncates v to s decimal places trunc(42.4382, 2) → 42.43
width_bucket ( operand numeric, low numeric, high numeric, count integer ) → integer width_bucket ( operand double precision, low double precision, high double precision, count integer ) → integer Returns the number of the bucket in which operand falls in a histogram having count equal-width buckets spanning the range low to high. Returns 0 or *count*+1 for an input outside that range. width_bucket(5.35, 0.024, 10.06, 5) → 3
width_bucket ( operand anycompatible, thresholds anycompatiblearray ) → integer Returns the number of the bucket in which operand falls given an array listing the lower bounds of the buckets. Returns 0 for an input less than the first lower bound. operand and the array elements can be of any type having standard comparison operators. The thresholds array must be sorted, smallest first, or unexpected results will be obtained. width_bucket(now(), array['yesterday', 'today', 'tomorrow']::timestamptz[]) → 2

Table 9.6 shows functions for generating random numbers.

Table 9.6. Random Functions

Function Description Example(s)
random ( ) → double precision Returns a random value in the range 0.0 <= x < 1.0 random() → 0.897124072839091
setseed ( double precision ) → void Sets the seed for subsequent random() calls; argument must be between -1.0 and 1.0, inclusive setseed(0.12345)

The random() function uses a simple linear congruential algorithm. It is fast but not suitable for cryptographic applications; see the pgcrypto module for a more secure alternative. If setseed() is called, the series of results of subsequent random() calls in the current session can be repeated by re-issuing setseed() with the same argument.

Table 9.7 shows the available trigonometric functions. Each of these functions comes in two variants, one that measures angles in radians and one that measures angles in degrees.

Table 9.7. Trigonometric Functions

Function Description Example(s)
acos ( double precision ) → double precision Inverse cosine, result in radians acos(1) → 0
acosd ( double precision ) → double precision Inverse cosine, result in degrees acosd(0.5) → 60
asin ( double precision ) → double precision Inverse sine, result in radians asin(1) → 1.5707963267948966
asind ( double precision ) → double precision Inverse sine, result in degrees asind(0.5) → 30
atan ( double precision ) → double precision Inverse tangent, result in radians atan(1) → 0.7853981633974483
atand ( double precision ) → double precision Inverse tangent, result in degrees atand(1) → 45
atan2 ( y double precision, x double precision ) → double precision Inverse tangent of y/x, result in radians atan2(1, 0) → 1.5707963267948966
atan2d ( y double precision, x double precision ) → double precision Inverse tangent of y/x, result in degrees atan2d(1, 0) → 90
cos ( double precision ) → double precision Cosine, argument in radians cos(0) → 1
cosd ( double precision ) → double precision Cosine, argument in degrees cosd(60) → 0.5
cot ( double precision ) → double precision Cotangent, argument in radians cot(0.5) → 1.830487721712452
cotd ( double precision ) → double precision Cotangent, argument in degrees cotd(45) → 1
sin ( double precision ) → double precision Sine, argument in radians sin(1) → 0.8414709848078965
sind ( double precision ) → double precision Sine, argument in degrees sind(30) → 0.5
tan ( double precision ) → double precision Tangent, argument in radians tan(1) → 1.5574077246549023
tand ( double precision ) → double precision Tangent, argument in degrees tand(45) → 1

Note

Another way to work with angles measured in degrees is to use the unit transformation functions radians() and degrees() shown earlier. However, using the degree-based trigonometric functions is preferred, as that way avoids round-off error for special cases such as sind(30).

Table 9.8 shows the available hyperbolic functions.

Table 9.8. Hyperbolic Functions

Function Description Example(s)
sinh ( double precision ) → double precision Hyperbolic sine sinh(1) → 1.1752011936438014
cosh ( double precision ) → double precision Hyperbolic cosine cosh(0) → 1
tanh ( double precision ) → double precision Hyperbolic tangent tanh(1) → 0.7615941559557649
asinh ( double precision ) → double precision Inverse hyperbolic sine asinh(1) → 0.881373587019543
acosh ( double precision ) → double precision Inverse hyperbolic cosine acosh(1) → 0
atanh ( double precision ) → double precision Inverse hyperbolic tangent atanh(0.5) → 0.5493061443340548