Conversion Functions - Ocient Documentation

conversion functions transform a specified operand to a different data type.

ST_ASBINARY

Alias of ST_ASWKB. Returns the well-known binary (WKB) representation of the specified geography. Syntax

SQL

ST_ASBINARY(geo [, XDR_or_NDR ] )

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, or `POLYGON`	The geospatial object used to calculate the dimensions.
`XDR_or_NDR`	`CHAR`	Optional. This argument determines whether the resulting WKB is in little endian (NDR) or big endian (XDR) format. If you specify this argument, it must be either `XDR` or `NDR`. Otherwise, it defaults to `NDR`.

Example

SQL

SELECT ST_ASBINARY(ST_POINT(2, 2), 'NDR');

Output: 010100000000000000000000400000000000000040

ST_ASGEOJSON

Returns the GeoJSON representation of the specified geography using the IETF standards.

SQL

 ST_ASGEOJSON( geo [, planar_conversion ] )

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, or `POLYGON`	The geospatial object used to create a GeoJSON representation. ℹ️ The GeoJSON specification has certain requirements for a `LINESTRING` and `POLYGON`. In keeping with this specification, a `POLYGON` instance that represents a `LINESTRING` results in a `LINESTRING` GeoJSON instance. Similarly, a `POLYGON` instance that represents a `POINT` results in a `POINT` GeoJSON instance. A `LINESTRING` instance that represents a `POINT` results in a `POINT` GeoJSON instance. Unlike the GeoJSON specification, a specified `POLYGON` does not need to follow the Right-Hand Rule. If a specified `POLYGON` contains any holes that are not valid `POLYGON` objects, then the function omits those holes in the resulting GeoJSON instance.
`planar_conversion`	`BOOLEAN`	Optional. A Boolean value that determines if the geodesic edges of the specified geography are converted to planar representation before the function applies the GeoJSON format. standards state that all GeoJSON objects are to be interpreted as explicitly planar. This argument allows preservation of the original geodesic shape. If `planar_conversion` is specified `TRUE`, points will be added such that the resulting GeoJSON represents a planar shape within 10m of the original geospatial object. Additionally, if the original geospatial object crossed the international dateline, it will be split at the point where it crosses. This will generate a GeoJSON object of either `MultiLineString` or `MultiPolygon` type, depending on the original type of the geospatial object. If you do not specify this argument, the value defaults to `FALSE`.

Examples This example converts a POINT value into a GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(ST_POINT(2, 2), false);

Output:

Text

{"type":"Point","coordinates":[2,2]}

This example converts an empty POINT value.

SQL

SELECT ST_ASGEOJSON(ST_POINTFROMTEXT('POINT EMPTY'), false);

Output:

Text

{"type":"Point","coordinates":[]}

This example converts a LINESTRING value into a GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(ST_LINESTRING(ST_POINT(1.234, 2),ST_POINT(3.456, 5));

Output:

Text

{"type":"LineString","coordinates":[[1.234,2],[3.456,5]]}

This example again converts a LINESTRING value.

SQL

SELECT ST_ASGEOJSON(ST_LINESTRING(ARRAY[ST_POINT(1.234, 2)]);

Output:

Text

{"type":"Point","coordinates":[1.234,2]}

This example converts an empty LINESTRING value into a GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(ST_LINEFROMTEXT('LINESTRING EMPTY'), false);

Output:

Text

{"type":"LineString","coordinates":[]}

This example converts a POLYGON value into a GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(
    ST_POLYGON(
        ARRAY [ST_POINT(1.234, 2),ST_POINT(3.456, 5),ST_POINT(5.678,         2),ST_POINT(1.234, 2)],
        ARRAY [ARRAY[ST_POINT(2,2.5),ST_POINT(2.1,2.6),ST_POINT(2.2,2.5),ST_POINT(2,2.5)],
        ARRAY [ST_POINT(3,2.5),ST_POINT(3.1,2.6),ST_POINT(3.2,2.5),ST_POINT(3,2.5)]]), false);

Output:

Text

{"type":"Polygon","coordinates":[[[1.234,2],[3.456,5],[5.678,2],[1.234,2]],[[2,2.5],[2.1,2.6],[2.2,2.5],[2,2.5]],[[3,2.5],[3.1,2.6],[3.2,2.5],[3,2.5]]]}

This example again converts a POLYGON value.

SQL

SELECT ST_ASGEOJSON(
    ST_POLYGON(
        ARRAY [ST_POINT(1.234, 2),ST_POINT(3.456, 5),ST_POINT(5.678, 2),ST_POINT(1.234, 2)],
        ARRAY [ARRAY[ST_POINT(2,2.5),ST_POINT(2.1,2.6),ST_POINT(2.2,2.5),ST_POINT(3,2.5)],
        ARRAY [ST_POINT(3,2.5),ST_POINT(3.2,2.5),ST_POINT(3,2.5)]]), false);

Output:

Text

{"type":"Polygon","coordinates":[[[1.234,2],[3.456,5],[5.678,2],[1.234,2]]]}

This example converts a two-point POLYGON, which results in a LINESTRING type in the GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(
        ST_POLYGON(
            ST_LINESTRING(ST_POINT(1.234, 2), ST_POINT(3.456, 5))),
        false);

Output:

Text

{"type":"LineString","coordinates":[[1.234,2],[3.456,5]]}

This example converts a single-point POLYGON, which results in a POINT type in the GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(ST_POLYGON(ST_POINT(1.234, 2)), false);

Output:

Text

{"type":"Point","coordinates":[1.234,2]}

This example converts an empty POLYGON value into a GeoJSON representation.

SQL

SELECT ST_ASGEOJSON(ST_POLYGONFROMTEXT('POLYGON EMPTY'), false);

Output:

Text

{"type":"Polygon","coordinates":[]}

ST_ASLATLONTEXT

Returns a string that represents geographic coordinates of a specified POINT in the specified format.

SQL

ST_ASLATLONTEXT(point, [ output_format ] )

Argument	Data Type	Description
`point`	`POINT`	A POINT value used to calculate geographic coordinates. If `point` is NULL, then this function returns NULL.
`output_format`	`CHAR`	Optional. A string that includes option flags to set the format and decimal precision for the output of the coordinates. Option flags must be uppercase to be recognized. Accepted option flags are: `D` — Represents coordinate degrees. If you specify a format string for `output_format`, this value is required. If `M` is omitted, this option flag sets the decimal precision. `M` — Represents minutes of latitude or longitude distance. If `S` is omitted, this option flag sets the decimal precision. `S` — Represents seconds of latitude or longitude distance. `C` — Represents the cardinal direction. If you specify this value, the appropriate cardinal direction is represented as N/S/E/W. If you omit this value, coordinates that are south or west are represented as negative values while east or north remain positive values. For all option flags besides `C`, you can repeat the option characters and use them with decimal points to set the format and decimal precision. The number of characters after the decimal point indicates the precision, while the number of characters before the decimal indicates the total width of the formatted number, including the decimal POINT. If the formatted number is shorter than the requested width, the system pads the value with leading spaces. Characters other than `D`, `M`, `S`, `C`, and `.` are passed through as string characters. If you do not specify `output_format` or leave it as empty, the value defaults to the format `D°M''S.SSS"C`.

Example

SQL

SELECT ST_ASLATLONTEXT(ST_POINT(10.2342342,-2.32498), 'D.D degrees MM.MM minutes C');

Output: '2.0 degrees 19.50 minutes S 10.0 degrees 14.05 minutes E'

ST_ASTEXT

Alias of ST_ASWKT and ST_EWKT. Returns the well-known text (WKT) representation of the specified geography. If you use ST_ASEWKT, the database prepends the resultant string with SRID=4326;.

SQL

ST_ASTEXT(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, or `POLYGON`	A geospatial object that is to be returned as a WKT value. If you specify a `LINESTRING` or `POLYGON` that contains a single `POINT`, the function returns the WKT representation as a `POINT`. If you specify a `POLYGON` that has an exterior that is not closed, the function returns the WKT representation as a `LINESTRING`.

Example

SQL

SELECT ST_ASTEXT(ST_POLYGON(ST_LINESTRING('LINESTRING(1 2, 1 3, 1 3, 1 2)')));

Output: POLYGON((1 2, 1 3, 1 3, 1 2))

ST_ASEWKT

For usage, see ST_ASTEXT.

ST_ASWKT

Alias of ST_ASTEXT.

ST_ASWKB

Alias of ST_ASBINARY.

ST_GEOHASH

Returns a string that represents the geohash of the input POINT. This function also accepts an optional second argument to specify the length of the geohash result. If you specify any argument as NULL, then the function returns NULL.

SQL

ST_GEOHASH(point [, precision ] )

Argument	Data Type	Description
`point`	`POINT`	A `POINT` value that is to be converted into a geohash.
`precision`	`INTEGER`	Optional. A numeric value that specifies the geohash precision, which determines the length of the output string. This number must be in the range of 1 to 20. If you do not specify this value, `precision` defaults to 20.

Example

SQL

SELECT ST_GEOHASH(ST_POINT(-126, 48));

Output: c0w3hc0w3hf1s70w3hf1s70w3 Geospatial Data Types Attribute Functions

​ST_ASBINARY

​ST_ASGEOJSON

​ST_ASLATLONTEXT

​ST_ASTEXT

​ST_ASEWKT

​ST_ASWKT

​ST_ASWKB

​ST_GEOHASH

​Related Links

ST_ASBINARY

ST_ASGEOJSON

ST_ASLATLONTEXT

ST_ASTEXT

ST_ASEWKT

ST_ASWKT

ST_ASWKB

ST_GEOHASH

Related Links