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* ISSUES-3890 sync system functions to en document * ISSUES-3890 fix review * ISSUES-3890 add parseDateTimeBestEffort docs * ISSUES-3890 fix review * ISSUES-3890 better sql example
74 lines
3.0 KiB
Markdown
74 lines
3.0 KiB
Markdown
# Rounding functions
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## floor(x\[, N\])
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Returns the largest round number that is less than or equal to x. A round number is a multiple of 1/10N, or the nearest number of the appropriate data type if 1 / 10N isn't exact.
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'N' is an integer constant, optional parameter. By default it is zero, which means to round to an integer.
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'N' may be negative.
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Examples: `floor(123.45, 1) = 123.4, floor(123.45, -1) = 120.`
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`x` is any numeric type. The result is a number of the same type.
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For integer arguments, it makes sense to round with a negative 'N' value (for non-negative 'N', the function doesn't do anything).
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If rounding causes overflow (for example, floor(-128, -1)), an implementation-specific result is returned.
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## ceil(x\[, N\]), ceiling(x\[, N\])
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Returns the smallest round number that is greater than or equal to 'x'. In every other way, it is the same as the 'floor' function (see above).
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## round(x\[, N\])
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Implements [banker's rounding](https://en.wikipedia.org/wiki/Rounding#Round_half_to_even), i.e., rounding to the nearest even integer.
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**Function arguments:**
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- `x` — the number to be rounded. [Type](../../data_types/index.md#data_types) — any number.
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- `N`— the position of the number after the decimal point to round the number to.
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**Returned value:**
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The rounded number of the same type as the input number `x`
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**Example:**
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``` sql
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SELECT
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number / 2 AS x,
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round(x)
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FROM system.numbers
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LIMIT 10
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```
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```
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┌───x─┬─round(divide(number, 2))─┐
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│ 0 │ 0 │
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│ 0.5 │ 0 │
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│ 1 │ 1 │
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│ 1.5 │ 2 │
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│ 2 │ 2 │
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│ 2.5 │ 2 │
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│ 3 │ 3 │
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│ 3.5 │ 4 │
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│ 4 │ 4 │
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│ 4.5 │ 4 │
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└─────┴──────────────────────────┘
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```
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## roundToExp2(num)
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Accepts a number. If the number is less than one, it returns 0. Otherwise, it rounds the number down to the nearest (whole non-negative) degree of two.
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## roundDuration(num)
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Accepts a number. If the number is less than one, it returns 0. Otherwise, it rounds the number down to numbers from the set: 1, 10, 30, 60, 120, 180, 240, 300, 600, 1200, 1800, 3600, 7200, 18000, 36000. This function is specific to Yandex.Metrica and used for implementing the report on session length
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## roundAge(num)
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Accepts a number. If the number is less than 18, it returns 0. Otherwise, it rounds the number down to a number from the set: 18, 25, 35, 45, 55. This function is specific to Yandex.Metrica and used for implementing the report on user age.
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## roundDown(num, arr)
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Accept a number, round it down to an element in the specified array. If the value is less than the lowest bound, the lowest bound is returned.
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[Original article](https://clickhouse.yandex/docs/en/query_language/functions/rounding_functions/) <!--hide-->
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