Well-known text representation in an SQL editor
Since the well-known text representation is text, it can
be typed into an SQL script or directly into an SQL editor. The text
is converted to and from a geometry by a function. Functions that
convert text to geometry have the following syntax:
function ('text description',SRID)Example:
ST_PointFromText('point zm (10.01 20.04 3.2 9.5)', 1)The spatial reference identifier, SRID—the primary key to the spatial_references table—identifies the possible spatial reference systems within the HCL® Informix® instance. An SRID is assigned to a spatial column when it is created. Before a geometry can be inserted into a spatial column, its SRID must match the SRID of the spatial column.
The text description is
made up of three basic components enclosed in single quotation marks:
'geometry type [coordinate type] [coordinate list]'The geometry type is defined as one of the following: point, linestring, polygon, multipoint, multilinestring, or multipolygon.
The coordinate type specifies whether the geometry has Z coordinates or measures. Leave this argument blank if the geometry has neither; otherwise, set the coordinate type to Z for geometries containing Z coordinates, M for geometries with measures, and ZM for geometries that have both.
The coordinate list defines the double-precision vertices of the geometry. Coordinate lists are comma-delimited and enclosed by parentheses. Geometries having multiple components require sets of parentheses to enclose each component part. If the geometry is empty, the EMPTY keyword replaces the coordinates.
The following examples provide a complete list of all
possible permutations of the text description portion of the text
representation.
| Geometry type | Text description | Comment |
|---|---|---|
| ST_Point | ‘point empty' | Empty point |
| ST_Point | ‘point z empty' | Empty point with Z coordinate |
| ST_Point | ‘point m empty' | Empty point with measure |
| ST_Point | ‘point zm empty' | Empty point with Z coordinate and measure |
| ST_Point | ‘point ( 10.05 10.28 )' | Point |
| ST_Point | ‘point z ( 10.05 10.28 2.51 )' | Point with Z coordinate |
| ST_Point | ‘point m ( 10.05 10.28 4.72 )' | Point with measure |
| ST_Point | ‘point zm ( 10.05 10.28 2.51 4.72 )' | Point with Z coordinate and measure |
| ST_LineString | ‘linestring empty' | Empty linestring |
| ST_LineString | ‘linestring z empty' | Empty linestring with Z coordinates |
| ST_LineString | ‘linestring m empty' | Empty linestring with measures |
| ST_LineString | ‘linestring zm empty' | Empty linestring with Z coordinates and measures |
| ST_LineString | ‘linestring ( 10.05 10.28 , 20.95 20.89 )' | Linestring |
| ST_LineString | ‘linestring z ( 10.05 10.28 3.09, 20.95 31.98 4.72, 21.98 29.80 3.51 )' | Linestring with Z coordinates |
| ST_LineString | ‘linestring m ( 10.05 10.28 5.84, 20.95 31.98 9.01, 21.98 29.80 12.84 )' | Linestring with measures |
| ST_LineString | ‘linestring zm (10.05 10.28 3.09 5.84, 20.95 31.98 4.72 9.01, 21.98 29.80 3.51 12.84)' | Linestring with Z coordinates and measures |
| ST_Polygon | ‘polygon empty' | Empty polygon |
| ST_Polygon | ‘polygon z empty' | Empty polygon with Z coordinates |
| ST_Polygon | ‘polygon m empty | Empty polygon with measures |
| ST_Polygon | ‘polygon zm empty' | Empty polygon with Z coordinates and measures |
| ST_Polygon | ‘polygon (( 10 10, 10 20, 20 20, 20 15, 10 10))' | Polygon |
| ST_Polygon | ‘polygon z ((10 10 3, 10 20 3, 20 20 3, 20 15 4, 10 10 3))' | Polygon with Z coordinates |
| ST_Polygon | ‘polygon m (( 10 10 8, 10 20 9, 20 20 9, 20 15 9, 10 10 8 ))' | Polygon with measures |
| ST_Polygon | ‘polygon zm (( 10 10 3 8, 10 20 3 9, 20 20 3 9, 20 15 4 9, 10 10 3 8 ))' | Polygon with Z coordinates and measures |
| ST_MultiPoint | ‘multipoint empty' | Empty multipoint |
| ST_MultiPoint | ‘multipoint z empty' | Empty multipoint with Z coordinates |
| ST_MultiPoint | ‘multipoint m empty' | Empty multipoint with measures |
| ST_MultiPoint | ‘multipoint zm empty' | Empty multipoint with Z coordinates and measures |
| ST_MultiPoint | ‘multipoint (10 10, 20 20)' | Multipoint with two points |
| ST_MultiPoint | ‘multipoint z (10 10 2, 20 20 3)' | Multipoint with Z coordinates |
| ST_MultiPoint | ‘multipoint m (10 10 4, 20 20 5)' | Multipoint with measures |
| ST_MultiPoint | ‘multipoint zm (10 10 2 4, 20 20 3 5)' | Multipoint with Z coordinates and measures |
| ST_MultiLineString | ‘multilinestring empty' | Empty multilinestring |
| ST_MultiLineString | ‘multilinestring z empty' | Empty multilinestring with Z coordinates |
| ST_MultiLineString | ‘multilinestring m empty' | Empty multilinestring with measures |
| ST_MultiLineString | ‘multilinestring zm empty' | Empty multilinestring with Z coordinates and measures |
| ST_MultiLineString | ‘multilinestring (( 10.05 10.28 , 20.95 20.89 ),( 20.95 20.89, 31.92 21.45))' | Multilinestring |
| ST_MultiLineString | ‘multilinestring z ((10.05 10.28 3.4, 20.95 20.89 4.5),( 20.95 20.89 4.5, 31.92 21.45 3.6))' | Multilinestring with Z coordinates |
| ST_MultiLineString | ‘multilinestring m ((10.05 10.28 8.4, 20.95 20.89 9.5),( 20.95 20.89 9.5, 31.92 21.45 8.6))' | Multilinestring with measures |
| ST_MultiLineString | ‘multilinestring zm ((10.05 10.28 3.4 8.4, 20.95 20.89 4.5 9.5), ( 20.95 20.89 4.5 9.5, 31.92 21.45 3.6 8.6))' | Multilinestring with Z coordinates and measures |
| ST_MultiPolygon | ‘multipolygon empty' | Empty multipolygon |
| ST_MultiPolygon | ‘multipolygon z empty' | Empty multipolygon with Z coordinates |
| ST_MultiPolygon | ‘multipolygon m empty' | Empty multipolygon with measures |
| ST_MultiPolygon | ‘multipolygon zm empty' | Empty multipolygon with Z coordinates and measures |
| ST_MultiPolygon | ‘multipolygon (((10 10, 10 20, 20 20, 20 15 , 10 10), (50 40, 50 50, 60 50, 60 40, 50 40)))' | Multipolygon |
| ST_MultiPolygon | ‘multipolygon z (((10 10 7, 10 20 8, 20 20 7, 20 15 5, 10 10 7), (50 40 6, 50 50 6, 60 50 5, 60 40 6, 50 40 7)))' | Multipolygon with Z coordinates |
| ST_MultiPolygon | ‘multipolygon m (((10 10 2, 10 20 3, 20 20 4, 20 15 5, 10 10 2), (50 40 7, 50 50 3, 60 50 4, 60 40 5, 50 40 7)))' | Multipolygon with measures |
| ST_MultiPolygon | ‘multipolygon zm (((10 10 7 2, 10 20 8 3, 20 20 7 4, 20 15 5 5, 10 10 7 2), (50 40 6 7, 50 50 6 3, 60 50 5 4, 60 40 6 5, 50 40 7 7)))' | Multipolygon with Z coordinates and measures |