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708 lines
16 KiB
Markdown
708 lines
16 KiB
Markdown
---
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toc_title: H3 Indexes
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---
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# Functions for Working with H3 Indexes {#h3index}
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[H3](https://eng.uber.com/h3/) is a geographical indexing system where Earth’s surface divided into a grid of even hexagonal cells. This system is hierarchical, i. e. each hexagon on the top level ("parent") can be splitted into seven even but smaller ones ("children"), and so on.
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The level of the hierarchy is called `resolution` and can receive a value from `0` till `15`, where `0` is the `base` level with the largest and coarsest cells.
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A latitude and longitude pair can be transformed to a 64-bit H3 index, identifying a grid cell.
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The H3 index is used primarily for bucketing locations and other geospatial manipulations.
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The full description of the H3 system is available at [the Uber Engeneering site](https://eng.uber.com/h3/).
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## h3IsValid {#h3isvalid}
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Verifies whether the number is a valid [H3](#h3index) index.
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**Syntax**
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``` sql
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h3IsValid(h3index)
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```
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**Parameter**
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- `h3index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- 1 — The number is a valid H3 index.
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- 0 — The number is not a valid H3 index.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3IsValid(630814730351855103) AS h3IsValid;
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```
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Result:
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``` text
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┌─h3IsValid─┐
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│ 1 │
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└───────────┘
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```
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## h3GetResolution {#h3getresolution}
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Defines the resolution of the given [H3](#h3index) index.
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**Syntax**
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``` sql
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h3GetResolution(h3index)
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```
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**Parameter**
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- `h3index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- Index resolution. Range: `[0, 15]`.
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- If the index is not valid, the function returns a random value. Use [h3IsValid](#h3isvalid) to verify the index.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3GetResolution(639821929606596015) AS resolution;
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```
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Result:
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``` text
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┌─resolution─┐
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│ 14 │
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└────────────┘
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```
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## h3EdgeAngle {#h3edgeangle}
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Calculates the average length of the [H3](#h3index) hexagon edge in grades.
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**Syntax**
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``` sql
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h3EdgeAngle(resolution)
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```
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**Parameter**
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- `resolution` — Index resolution. Type: [UInt8](../../../sql-reference/data-types/int-uint.md). Range: `[0, 15]`.
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**Returned values**
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- The average length of the [H3](#h3index) hexagon edge in grades. Type: [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT h3EdgeAngle(10) AS edgeAngle;
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```
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Result:
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``` text
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┌───────h3EdgeAngle(10)─┐
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│ 0.0005927224846720883 │
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└───────────────────────┘
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```
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## h3EdgeLengthM {#h3edgelengthm}
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Calculates the average length of the [H3](#h3index) hexagon edge in meters.
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**Syntax**
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``` sql
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h3EdgeLengthM(resolution)
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```
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**Parameter**
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- `resolution` — Index resolution. Type: [UInt8](../../../sql-reference/data-types/int-uint.md). Range: `[0, 15]`.
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**Returned values**
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- The average length of the [H3](#h3index) hexagon edge in meters. Type: [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT h3EdgeLengthM(15) AS edgeLengthM;
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```
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Result:
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``` text
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┌─edgeLengthM─┐
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│ 0.509713273 │
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└─────────────┘
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```
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## geoToH3 {#geotoh3}
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Returns [H3](#h3index) point index `(lon, lat)` with specified resolution.
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**Syntax**
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``` sql
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geoToH3(lon, lat, resolution)
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```
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**Arguments**
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- `lon` — Longitude. Type: [Float64](../../../sql-reference/data-types/float.md).
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- `lat` — Latitude. Type: [Float64](../../../sql-reference/data-types/float.md).
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- `resolution` — Index resolution. Range: `[0, 15]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- Hexagon index number.
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- 0 in case of error.
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Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT geoToH3(37.79506683, 55.71290588, 15) AS h3Index;
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```
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Result:
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``` text
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┌────────────h3Index─┐
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│ 644325524701193974 │
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└────────────────────┘
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```
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## h3ToGeo {#h3togeo}
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Returns the geographical coordinates of longitude and latitude corresponding to the provided [H3](#h3index) index.
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**Syntax**
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``` sql
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h3ToGeo(h3Index)
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```
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**Arguments**
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- `h3Index` — H3 Index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- A tuple consisting of two values: `tuple(lon,lat)`. `lon` — Longitude. [Float64](../../../sql-reference/data-types/float.md). `lat` — Latitude. [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT h3ToGeo(644325524701193974) AS coordinates;
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```
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Result:
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``` text
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┌─coordinates───────────────────────────┐
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│ (37.79506616830252,55.71290243145668) │
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└───────────────────────────────────────┘
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```
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## h3ToGeoBoundary {#h3togeoboundary}
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Returns array of pairs `(lon, lat)`, which corresponds to the boundary of the provided H3 index.
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**Syntax**
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``` sql
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h3ToGeoBoundary(h3Index)
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```
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**Arguments**
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- `h3Index` — H3 Index. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- Array of pairs '(lon, lat)'.
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Type: [Array](../../../sql-reference/data-types/array.md)([Float64](../../../sql-reference/data-types/float.md), [Float64](../../../sql-reference/data-types/float.md)).
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**Example**
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Query:
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``` sql
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SELECT h3ToGeoBoundary(644325524701193974) AS coordinates;
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```
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Result:
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``` text
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┌─h3ToGeoBoundary(599686042433355775)────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ [(37.2713558667319,-121.91508032705622),(37.353926450852256,-121.8622232890249),(37.42834118609435,-121.92354999630156),(37.42012867767779,-122.03773496427027),(37.33755608435299,-122.090428929044),(37.26319797461824,-122.02910130919001)] │
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└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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## h3kRing {#h3kring}
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Lists all the [H3](#h3index) hexagons in the raduis of `k` from the given hexagon in random order.
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**Syntax**
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``` sql
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h3kRing(h3index, k)
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```
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**Arguments**
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- `h3index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `k` — Raduis. Type: [integer](../../../sql-reference/data-types/int-uint.md)
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**Returned values**
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- Array of H3 indexes.
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Type: [Array](../../../sql-reference/data-types/array.md)([UInt64](../../../sql-reference/data-types/int-uint.md)).
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**Example**
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Query:
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``` sql
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SELECT arrayJoin(h3kRing(644325529233966508, 1)) AS h3index;
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```
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Result:
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``` text
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┌────────────h3index─┐
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│ 644325529233966508 │
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│ 644325529233966497 │
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│ 644325529233966510 │
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│ 644325529233966504 │
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│ 644325529233966509 │
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│ 644325529233966355 │
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│ 644325529233966354 │
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└────────────────────┘
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```
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## h3GetBaseCell {#h3getbasecell}
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Returns the base cell number of the [H3](#h3index) index.
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**Syntax**
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``` sql
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h3GetBaseCell(index)
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```
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**Parameter**
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- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- Hexagon base cell number.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3GetBaseCell(612916788725809151) AS basecell;
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```
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Result:
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``` text
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┌─basecell─┐
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│ 12 │
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└──────────┘
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```
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## h3HexAreaM2 {#h3hexaream2}
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Returns average hexagon area in square meters at the given resolution.
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**Syntax**
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``` sql
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h3HexAreaM2(resolution)
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```
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**Parameter**
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- `resolution` — Index resolution. Range: `[0, 15]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- Area in square meters.
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Type: [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT h3HexAreaM2(13) AS area;
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```
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Result:
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``` text
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┌─area─┐
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│ 43.9 │
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└──────┘
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```
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## h3IndexesAreNeighbors {#h3indexesareneighbors}
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Returns whether or not the provided [H3](#h3index) indexes are neighbors.
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**Syntax**
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``` sql
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h3IndexesAreNeighbors(index1, index2)
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```
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**Arguments**
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- `index1` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `index2` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- `1` — Indexes are neighbours.
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- `0` — Indexes are not neighbours.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3IndexesAreNeighbors(617420388351344639, 617420388352655359) AS n;
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```
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Result:
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``` text
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┌─n─┐
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│ 1 │
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└───┘
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```
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## h3ToChildren {#h3tochildren}
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Returns an array of child indexes for the given [H3](#h3index) index.
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**Syntax**
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``` sql
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h3ToChildren(index, resolution)
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```
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**Arguments**
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- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `resolution` — Index resolution. Range: `[0, 15]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- Array of the child H3-indexes.
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Type: [Array](../../../sql-reference/data-types/array.md)([UInt64](../../../sql-reference/data-types/int-uint.md)).
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**Example**
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Query:
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``` sql
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SELECT h3ToChildren(599405990164561919, 6) AS children;
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```
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Result:
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``` text
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┌─children───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
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│ [603909588852408319,603909588986626047,603909589120843775,603909589255061503,603909589389279231,603909589523496959,603909589657714687] │
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└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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## h3ToParent {#h3toparent}
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Returns the parent (coarser) index containing the given [H3](#h3index) index.
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**Syntax**
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``` sql
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h3ToParent(index, resolution)
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```
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**Arguments**
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- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `resolution` — Index resolution. Range: `[0, 15]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- Parent H3 index.
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Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3ToParent(599405990164561919, 3) AS parent;
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```
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Result:
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``` text
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┌─────────────parent─┐
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│ 590398848891879423 │
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└────────────────────┘
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```
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## h3ToString {#h3tostring}
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Converts the `H3Index` representation of the index to the string representation.
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``` sql
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h3ToString(index)
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```
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**Parameter**
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- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- String representation of the H3 index.
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Type: [String](../../../sql-reference/data-types/string.md).
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**Example**
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Query:
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``` sql
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SELECT h3ToString(617420388352917503) AS h3_string;
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```
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Result:
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``` text
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┌─h3_string───────┐
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│ 89184926cdbffff │
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└─────────────────┘
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```
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## stringToH3 {#stringtoh3}
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Converts the string representation to the `H3Index` (UInt64) representation.
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**Syntax**
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``` sql
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stringToH3(index_str)
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```
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**Parameter**
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- `index_str` — String representation of the H3 index. Type: [String](../../../sql-reference/data-types/string.md).
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**Returned value**
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- Hexagon index number. Returns 0 on error. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT stringToH3('89184926cc3ffff') AS index;
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```
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Result:
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``` text
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┌──────────────index─┐
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│ 617420388351344639 │
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└────────────────────┘
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```
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## h3GetResolution {#h3getresolution}
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Returns the resolution of the [H3](#h3index) index.
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**Syntax**
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``` sql
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h3GetResolution(index)
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```
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**Parameter**
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- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned value**
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- Index resolution. Range: `[0, 15]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT h3GetResolution(617420388352917503) AS res;
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```
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Result:
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``` text
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┌─res─┐
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│ 9 │
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└─────┘
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```
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## h3IsResClassIII {#h3isresclassIII}
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|
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Returns whether [H3](#h3index) index has a resolution with Class III orientation.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
h3IsResClassIII(index)
|
||
```
|
||
|
||
**Parameter**
|
||
|
||
- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Returned value**
|
||
|
||
- `1` — Index has a resolution with Class III orientation.
|
||
- `0` — Index doesn't have a resolution with Class III orientation.
|
||
|
||
Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT h3IsResClassIII(617420388352917503) AS res;
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─res─┐
|
||
│ 1 │
|
||
└─────┘
|
||
```
|
||
|
||
## h3IsPentagon {#h3ispentagon}
|
||
|
||
Returns whether this [H3](#h3index) index represents a pentagonal cell.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
h3IsPentagon(index)
|
||
```
|
||
|
||
**Parameter**
|
||
|
||
- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Returned value**
|
||
|
||
- `1` — Index represents a pentagonal cell.
|
||
- `0` — Index doesn't represent a pentagonal cell.
|
||
|
||
Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT h3IsPentagon(644721767722457330) AS pentagon;
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─pentagon─┐
|
||
│ 0 │
|
||
└──────────┘
|
||
```
|
||
|
||
## h3GetFaces {#h3getfaces}
|
||
|
||
Returns icosahedron faces intersected by a given [H3](#h3index) index.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
h3GetFaces(index)
|
||
```
|
||
|
||
**Parameter**
|
||
|
||
- `index` — Hexagon index number. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
**Returned values**
|
||
|
||
- Array containing icosahedron faces intersected by a given H3 index.
|
||
|
||
Type: [Array](../../../sql-reference/data-types/array.md)([UInt64](../../../sql-reference/data-types/int-uint.md)).
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT h3GetFaces(599686042433355775) AS faces;
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─faces─┐
|
||
│ [7] │
|
||
└───────┘
|
||
```
|
||
|
||
[Original article](https://clickhouse.com/docs/en/sql-reference/functions/geo/h3) <!--hide-->
|