ClickHouse/docs/en/query_language/functions/rounding_functions.md
Ivan Blinkov 0a4a5b36cc
Some WIP on documentation refactoring (#2659)
* Additional .gitignore entries

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* Adapt table with formats to English docs too

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* Move Data types higher in ToC

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* Few fixes for en/table_engines/file.md

* Use smaller header sizes in changelogs

* Group up table engines inside ToC

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* Specificy in ToC that query language is SQL based. Thats a bit excessive, but catches eye.

* Move stuff that is part of query language into respective folder

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* Lost redirects.txt update

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* Extract major parts of queries.md into separate articles

* queries.md has been supposed to be removed

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* There is only table of contents left

* "Query language" is actually part of SQL abbreviation

* Change filename in README.md too

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2018-07-18 13:00:53 +03:00

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# Rounding functions
## floor(x\[, N\])
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.
'N' is an integer constant, optional parameter. By default it is zero, which means to round to an integer.
'N' may be negative.
Examples: `floor(123.45, 1) = 123.4, floor(123.45, -1) = 120.`
`x` is any numeric type. The result is a number of the same type.
For integer arguments, it makes sense to round with a negative 'N' value (for non-negative 'N', the function doesn't do anything).
If rounding causes overflow (for example, floor(-128, -1)), an implementation-specific result is returned.
## ceil(x\[, N\])
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).
## round(x\[, N\])
Returns the round number nearest to 'num', which may be less than, greater than, or equal to 'x'.If 'x' is exactly in the middle between the nearest round numbers, one of them is returned (implementation-specific).
The number '-0.' may or may not be considered round (implementation-specific).
In every other way, this function is the same as 'floor' and 'ceil' described above.
## roundToExp2(num)
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.
## roundDuration(num)
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
## roundAge(num)
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.