12.16.3 Functions That Create Geometry Values from WKT Values

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These functions take as arguments a Well-Known Text (WKT) representation and, optionally, a spatial reference system identifier (SRID). They return the corresponding geometry. For a description of WKT format, see Well-Known Text (WKT) Format.

Functions in this section detect arguments in either Cartesian or geographic spatial reference systems (SRSs), and return results appropriate to the SRS.

ST_GeomFromText() accepts a WKT value of any geometry type as its first argument. Other functions provide type-specific construction functions for construction of geometry values of each geometry type.

Functions such as ST_MPointFromText() and ST_GeomFromText() that accept WKT-format representations of MultiPoint values permit individual points within values to be surrounded by parentheses. For example, both of the following function calls are valid:

ST_MPointFromText('MULTIPOINT (1 1, 2 2, 3 3)')
ST_MPointFromText('MULTIPOINT ((1 1), (2 2), (3 3))')

Functions such as ST_GeomFromText() that accept WKT geometry collection arguments understand both OpenGIS 'GEOMETRYCOLLECTION EMPTY' standard syntax and MySQL 'GEOMETRYCOLLECTION()' nonstandard syntax. Functions such as ST_AsWKT() that produce WKT values produce 'GEOMETRYCOLLECTION EMPTY' standard syntax:

mysql> SET @s1 = ST_GeomFromText('GEOMETRYCOLLECTION()');
mysql> SET @s2 = ST_GeomFromText('GEOMETRYCOLLECTION EMPTY');
mysql> SELECT ST_AsWKT(@s1), ST_AsWKT(@s2);
+--------------------------+--------------------------+
| ST_AsWKT(@s1) | ST_AsWKT(@s2) |
+--------------------------+--------------------------+
| GEOMETRYCOLLECTION EMPTY | GEOMETRYCOLLECTION EMPTY |
+--------------------------+--------------------------+

Unless otherwise specified, functions in this section handle their arguments as follows:

If any geometry argument is NULL or is not a syntactically well-formed geometry, or if the SRID argument is NULL, the return value is NULL.
By default, geographic coordinates (latitude, longitude) are interpreted as in the order specified by the spatial reference system of geometry arguments. An optional options argument may be given to override the default axis order. options consists of a list of comma-separated key=value. The onlypermitted key value is axis-order, with permitted values of lat-long, long-lat and srid-defined (the default).
If the options argument is NULL, the return value is NULL. If the options argument is invalid, an error occurs to indicate why.
If an SRID argument refers to an undefined spatial reference system (SRS), an ER_SRS_NOT_FOUND error occurs.
For geographic SRS geometry arguments, if any argument has a longitude or latitude that is out of range, an error occurs:
- If a longitude value is not in the range (−180, 180], an ER_LONGITUDE_OUT_OF_RANGE error occurs.
- If a latitude value is not in the range [−90, 90], an ER_LATITUDE_OUT_OF_RANGE error occurs.
Ranges shown are in degrees. If an SRS uses another unit, the range uses the corresponding values in its unit. The exact range limits deviate slightly due to floating-point arithmetic.

These functions are available for creating geometries from WKT values:

ST_GeomCollFromText(wkt[, srid [, options]]), ST_GeometryCollectionFromText(wkt[, srid [, options]]), ST_GeomCollFromTxt(wkt[, srid [, options]])
Constructs a GeometryCollection value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
1. mysql> SET @g = "MULTILINESTRING((10 10, 11 11), (9 9, 10 10))";
2. mysql> SELECT ST_AsText(ST_GeomCollFromText(@g));
3. +--------------------------------------------+
4. | ST_AsText(ST_GeomCollFromText(@g)) |
5. +--------------------------------------------+
6. | MULTILINESTRING((10 10,11 11),(9 9,10 10)) |
7. +--------------------------------------------+
ST_GeomFromText(wkt[, srid [, options]]), ST_GeometryFromText(wkt[, srid [, options]])
Constructs a geometry value of any type using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
ST_LineFromText(wkt[, srid [, options]]), ST_LineStringFromText(wkt[, srid [, options]])
Constructs a LineString value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
ST_MLineFromText(wkt[, srid [, options]]), ST_MultiLineStringFromText(wkt[, srid [, options]])
Constructs a MultiLineString value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
ST_MPointFromText(wkt[, srid [, options]]), ST_MultiPointFromText(wkt[, srid [, options]])
Constructs a MultiPoint value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
ST_MPolyFromText(wkt[, srid [, options]]), ST_MultiPolygonFromText(wkt[, srid [, options]])
Constructs a MultiPolygon value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.
ST_PointFromText(wkt[, srid [, options]])
Constructs a Point value using its WKT representation and SRID.
ST_PointFromText() handles its arguments as described in the introduction to this section.
ST_PolyFromText(wkt[, srid [, options]]), ST_PolygonFromText(wkt[, srid [, options]])
Constructs a Polygon value using its WKT representation and SRID.
These functions handle their arguments as described in the introduction to this section.

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Dokument erstellt 26/06/2006, zuletzt geändert 26/10/2018
Quelle des gedruckten Dokuments:https://www.gaudry.be/de/mysql-rf-gis-wkt-functions.html

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