Rounding

round

Rounds a value to a specified number of decimal places N.

If N > 0, the function rounds to the right of the decimal point.
If N < 0, the function rounds to the left of the decimal point.
If N = 0, the function rounds to the next integer.

The function returns the nearest number of the specified order. If the input value has equal distance to two neighboring numbers, the function uses banker's rounding for Float* inputs and rounds away from zero for the other number types (Decimal*).

If rounding causes an overflow (for example, round(255, -1)), the result is undefined.

Syntax

round(x[, N])

Arguments

x — A number to round. Float* or Decimal* or (U)Int*
N — Optional. The number of decimal places to round to. Defaults to 0. (U)Int*

Returned value

Returns a rounded number of the same type as x. Float* or Decimal* or (U)Int*

Examples

Float inputs

SELECT number / 2 AS x, round(x) FROM system.numbers LIMIT 3;

┌───x─┬─round(x)─┐
│   0 │        0 │
│ 0.5 │        0 │
│   1 │        1 │
└─────┴──────────┘

Decimal inputs

SELECT cast(number / 2 AS  Decimal(10,4)) AS x, round(x) FROM system.numbers LIMIT 3;

┌───x─┬─round(x)─┐
│   0 │        0 │
│ 0.5 │        1 │
│   1 │        1 │
└─────┴──────────┘

Introduced in version 1.1.

roundAge

Takes a number representing a human age, compares it to standard age ranges, and returns either the highest or lowest value of the range the number falls within.

Returns 0, for age < 1.
Returns 17, for 1 ≤ age ≤ 17.
Returns 18, for 18 ≤ age ≤ 24.
Returns 25, for 25 ≤ age ≤ 34.
Returns 35, for 35 ≤ age ≤ 44.
Returns 45, for 45 ≤ age ≤ 54.
Returns 55, for age ≥ 55.

Syntax

roundAge(num)

Arguments

age — A number representing an age in years. (U)Int* or Float*

Returned value

Returns either the highest or lowest age of the range age falls within. UInt8

Examples

Usage example

SELECT *, roundAge(*) FROM system.numbers WHERE number IN (0, 5, 20, 31, 37, 54, 72);

┌─number─┬─roundAge(number)─┐
│      0 │                0 │
│      5 │               17 │
│     20 │               18 │
│     31 │               25 │
│     37 │               35 │
│     54 │               45 │
│     72 │               55 │
└────────┴──────────────────┘

Introduced in version 1.1.

roundBankers

Rounds a number to a specified decimal position N. If the rounding number is halfway between two numbers, the function uses a method of rounding called banker's rounding, which is the default rounding method for floating point numbers defined in IEEE 754.

If N > 0, the function rounds to the right of the decimal point
If N < 0, the function rounds to the left of the decimal point
If N = 0, the function rounds to the next integer

:::info Notes

When the rounding number is halfway between two numbers, it's rounded to the nearest even digit at the specified decimal position. For example: 3.5 rounds up to 4, 2.5 rounds down to 2.
The round function performs the same rounding for floating point numbers.
The roundBankers function also rounds integers the same way, for example, roundBankers(45, -1) = 40.
In other cases, the function rounds numbers to the nearest integer. :::

:::tip Use banker's rounding for summation or subtraction of numbers Using banker's rounding, you can reduce the effect that rounding numbers has on the results of summing or subtracting these numbers.

For example, sum numbers 1.5, 2.5, 3.5, 4.5 with different rounding:

No rounding: 1.5 + 2.5 + 3.5 + 4.5 = 12.
Banker's rounding: 2 + 2 + 4 + 4 = 12.
Rounding to the nearest integer: 2 + 3 + 4 + 5 = 14. :::

Syntax

roundBankers(x[, N])

Arguments

x — A number to round. (U)Int* or Decimal* or Float*
[, N] — Optional. The number of decimal places to round to. Defaults to 0. (U)Int*

Returned value

Returns a value rounded by the banker's rounding method. (U)Int* or Decimal* or Float*

Examples

Basic usage

SELECT number / 2 AS x, roundBankers(x, 0) AS b FROM system.numbers LIMIT 10

┌───x─┬─b─┐
│   0 │ 0 │
│ 0.5 │ 0 │
│   1 │ 1 │
│ 1.5 │ 2 │
│   2 │ 2 │
│ 2.5 │ 2 │
│   3 │ 3 │
│ 3.5 │ 4 │
│   4 │ 4 │
│ 4.5 │ 4 │
└─────┴───┘

Introduced in version 20.1.

roundDown

Rounds a number down to an element in the specified array. If the value is less than the lower bound, the lower bound is returned.

Syntax

roundDown(num, arr)

Arguments

num — A number to round down. (U)Int* or Decimal* or Float*
arr — Array of elements to round num down to. Array((U)Int*) or Array(Float*)

Returned value

Returns a number rounded down to an element in arr. If the value is less than the lowest bound, the lowest bound is returned. (U)Int* or Float*

Examples

Usage example

SELECT *, roundDown(*, [3, 4, 5]) FROM system.numbers WHERE number IN (0, 1, 2, 3, 4, 5)

┌─number─┬─roundDown(number, [3, 4, 5])─┐
│      0 │                            3 │
│      1 │                            3 │
│      2 │                            3 │
│      3 │                            3 │
│      4 │                            4 │
│      5 │                            5 │
└────────┴──────────────────────────────┘

Introduced in version 20.1.

roundDuration

Rounds a number down to the closest from a set of commonly used durations: 1, 10, 30, 60, 120, 180, 240, 300, 600, 1200, 1800, 3600, 7200, 18000, 36000. If the number is less than one, it returns 0.

Syntax

roundDuration(num)

Arguments

num — A number to round to one of the numbers in the set of common durations. (U)Int* or Float*

Returned value

Returns 0, for num < 1. Otherwise, one of: 1, 10, 30, 60, 120, 180, 240, 300, 600, 1200, 1800, 3600, 7200, 18000, 36000. UInt16

Examples

Usage example

SELECT *, roundDuration(*) FROM system.numbers WHERE number IN (0, 9, 19, 47, 101, 149, 205, 271, 421, 789, 1423, 2345, 4567, 9876, 24680, 42573)

┌─number─┬─roundDuration(number)─┐
│      0 │                     0 │
│      9 │                     1 │
│     19 │                    10 │
│     47 │                    30 │
│    101 │                    60 │
│    149 │                   120 │
│    205 │                   180 │
│    271 │                   240 │
│    421 │                   300 │
│    789 │                   600 │
│   1423 │                  1200 │
│   2345 │                  1800 │
│   4567 │                  3600 │
│   9876 │                  7200 │
│  24680 │                 18000 │
│  42573 │                 36000 │
└────────┴───────────────────────┘

Introduced in version 1.1.

roundToExp2

Rounds a number down to the nearest (whole non-negative) power of two. If the number is less than one, it returns 0.

Syntax

roundToExp2(num)

Arguments

num — A number to round. (U)Int* or Float*

Returned value

Returns num rounded down to the nearest (whole non-negative) power of two, otherwise 0 for num < 1. (U)Int* or Float*

Examples

Usage example

SELECT *, roundToExp2(*) FROM system.numbers WHERE number IN (0, 2, 5, 10, 19, 50)

┌─number─┬─roundToExp2(number)─┐
│      0 │                   0 │
│      2 │                   2 │
│      5 │                   4 │
│     10 │                   8 │
│     19 │                  16 │
│     50 │                  32 │
└────────┴─────────────────────┘

Introduced in version 1.1.

trunc

Like floor but returns the rounded number with the largest absolute value less than or equal to that of x.

Syntax

truncate(x[, N])

Arguments

x — The value to round. Float* or Decimal* or (U)Int*
N — Optional. The number of decimal places to round to. Defaults to zero, which means rounding to an integer. (U)Int*

Returned value

Returns a rounded number of the same type as x. Float* or Decimal* or (U)Int*

Examples

Basic usage

SELECT truncate(123.499, 1) AS res;

┌───res─┐
│ 123.4 │
└───────┘

Introduced in version 1.1.

ceil

floor

round

roundAge

roundBankers

roundDown

roundDuration

roundToExp2

trunc

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