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* Some improvements for introduction/performance.md
* Minor improvements for example_datasets
* Add website/package-lock.json to .gitignore
* YT paragraph was badly outdated and there is no real reason to write a new one
* Use weird introduction article as a starting point for F.A.Q.
* Some refactoring of first half of ya_metrika_task.md
* minor
* Weird docs footer bugfix
* Forgotten redirect
* h/v scrollbars same size in docs
* CLICKHOUSE-3831: introduce security changelog
* A bit more narrow tables on docs front page
* fix flag in ru docs
* Save some space in top level of docs ToC
* Capitalize most words in titles of docs/en/
* more docs scrollbar fixes
* fix incorrect merge
* fix link
* fix switching languages in single page docs mode
* Update mkdocs & mkdocs-material + unminify javascript
* cherrypick 17e18d1ecc
71 lines
1.8 KiB
Markdown
71 lines
1.8 KiB
Markdown
# Float32, Float64
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[Floating point numbers](https://en.wikipedia.org/wiki/IEEE_754).
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Types are equivalent to types of C:
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- `Float32` - `float`
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- `Float64` - `double`
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We recommend that you store data in integer form whenever possible. For example, convert fixed precision numbers to integer values, such as monetary amounts or page load times in milliseconds.
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## Using Floating-point Numbers
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- Computations with floating-point numbers might produce a rounding error.
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```sql
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SELECT 1 - 0.9
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```
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```
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┌───────minus(1, 0.9)─┐
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│ 0.09999999999999998 │
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└─────────────────────┘
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```
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- The result of the calculation depends on the calculation method (the processor type and architecture of the computer system).
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- Floating-point calculations might result in numbers such as infinity (`Inf`) and "not-a-number" (`NaN`). This should be taken into account when processing the results of calculations.
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- When reading floating point numbers from rows, the result might not be the nearest machine-representable number.
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## NaN and Inf
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In contrast to standard SQL, ClickHouse supports the following categories of floating-point numbers:
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- `Inf` – Infinity.
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```sql
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SELECT 0.5 / 0
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```
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```
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┌─divide(0.5, 0)─┐
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│ inf │
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└────────────────┘
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```
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- `-Inf` – Negative infinity.
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```sql
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SELECT -0.5 / 0
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```
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```
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┌─divide(-0.5, 0)─┐
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│ -inf │
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└─────────────────┘
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```
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- `NaN` – Not a number.
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```
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SELECT 0 / 0
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```
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```
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┌─divide(0, 0)─┐
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│ nan │
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└──────────────┘
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```
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See the rules for ` NaN` sorting in the section [ORDER BY clause](../query_language/select.md#query_language-queries-order_by).
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