Attribute Functions - Ocient Documentation

attribute functions return descriptive information on the specified data set.

ST_COORDDIM

Alias for ST_NDIMS or ST_NDIMENSION. Returns an INTEGER of the coordinate dimension of the specified geography. Syntax

SQL

ST_COORDDIM(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, or `POLYGON`	The geospatial object used to calculate the dimensions.

Example

SQL

SELECT ST_COORDDIM(ST_POLYGON('POLYGON((1 1, 2 1, 2 2, 1 1))'));

Output: 2

ST_DIMENSION

Returns an INTEGER that represents the dimension of the specified geography. This table describes the result values of the ST_DIMENSION function.

ST_DIMENSION Result Value	Dimension Type
`-1`	Empty geography value
`0`	`POINT`
`1`	`LINESTRING`
`2`	`POLYGON`

The ST_DIMENSION function always returns 0 for non-empty POINT objects. For non-empty LINESTRING and POLYGON objects, the ST_DIMENSION function returns the dimension value equal to the greatest dimension represented by their bounding points. For example, a LINESTRING or POLYGON object that contains only a single point returns 0. Similarly, a POLYGON object can return 1 if it contains insufficient points to represent a closed polygon. Syntax

SQL

ST_DIMENSION(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, or `POLYGON`	The geospatial object used to calculate the dimensions.

Examples In this example, the function evaluates a LINESTRING with an empty POINT value.

SQL

SELECT ST_DIMENSION(ST_LINESTRING('POINT EMPTY'));

Output: -1 In this example, the function evaluates a LINESTRING with a single POINT value.

SQL

SELECT ST_DIMENSION(ST_LINESTRING('ST_POINT(0 0)'));

Output: 0 This example evaluates an empty LINESTRING.

SQL

SELECT ST_DIMENSION(ST_LINESTRING('LINESTRING EMPTY'));

Output: -1 In this example, the function again evaluates a LINESTRING with a single POINT value.

SQL

SELECT ST_DIMENSION(ST_LINESTRING('LINESTRING(0 0)'));

Output: 0 In this example, the function evaluates a LINESTRING with multiple POINT values.

SQL

SELECT ST_DIMENSION(ST_LINESTRING('LINESTRING(0 0, 1 1)'));

Output: 1 This example evaluates an empty POLYGON.

SQL

SELECT ST_DIMENSION(ST_POLYGON('POLYGON EMPTY'));

Output: -1 This example evaluates a POLYGON with a single POINT.

SQL

SELECT ST_DIMENSION(ST_POLYGON('POLYGON((1 1))'));

Output: 0 This example evaluates a POLYGON with two POINT values.

SQL

SELECT ST_DIMENSION(ST_POLYGON('POLYGON((0 0, 1 1))'));

Output: 1 This example evaluates a POLYGON with multiple POINT values, enough to close the POLYGON.

SQL

SELECT ST_DIMENSION(ST_POLYGON('POLYGON((0 0, 1 0, 1 1, 0 0))'));

Output: 2

ST_GEOMETRYTYPE

Returns a STRING that represents the geometry of the input geospatial value. Supported values are ST_POINT, ST_LINESTRING, and ST_POLYGON. This function enforces the same strict dimension types as the ST_DIMENSION function. If geo is NULL, then the function returns NULL. Syntax

SQL

ST_GEOMETRYTYPE(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	A geospatial value to be identified by its dimension type.

Example

SQL

SELECT ST_GEOMETRYTYPE(ST_POINT(1, 2));

Output: ST_POINT

ST_ISEMPTY

Returns TRUE if the specified geography value is empty, such as 'POLYGON EMPTY'. A NULL input value returns NULL. Syntax

SQL

ST_ISEMPTY(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	A geospatial value to be examined if it is empty.

Example

SQL

SELECT ST_ISEMPTY(ST_POLYGON('POLYGON EMPTY'));

Output: TRUE

ST_MEMSIZE

Returns an INTEGER representing the number of bytes in memory required to store the specified geography. Syntax

SQL

ST_MEMSIZE(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	A geospatial value to be measured by its data memory.

Example

SQL

SELECT ST_MEMSIZE(ST_POINT(1,1));

Output: 16

ST_NDIMS or ST_NDIMENSION

Alias for ST_COORDDIM.

ST_NPOINTS or ST_NUMPOINTS

Returns an INTEGER representing the number of POINT values in a specified geography. If the specified value is a POLYGON, this function counts the number of POINT values in both the exterior and any holes. Syntax

SQL

ST_NPOINTS(geo)

SQL

ST_NUMPOINTS(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	A geospatial value to be examined for its count of `POINT` values.

Example

SQL

SELECT ST_NPOINTS(
   ST_POLYGON(
      'POLYGON((1 2, 1 3, 1 2))'));

Output: 3

ST_SRID

Returns the EPSG code of the spatial reference identifier (SRID) of the input geography. All geographies are of type GCS WGS 84, which is identified by the value 4326. There is no way to set a different SRID. Syntax

SQL

ST_SRID(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	A geospatial value to be analyzed for its EPSG code.

Example

SQL

SELECT ST_SRID(ST_MAKEPOINT(1.1, 3.11));

Output: 4326

ST_X

Returns the x value, or longitude, of the specified POINT. The returned value is a DOUBLE type. Syntax

SQL

ST_X(point)

Argument	Data Type	Description
`point`	`POINT`	A geospatial point to be analyzed for its x value, the longitude.

Example

SQL

SELECT ST_X(ST_POINT(3, 5));

Output: 3

ST_XMAX

Returns the maximum x value of the specified geography. The returned value is a DOUBLE type. Syntax

SQL

ST_XMAX(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	One or more geospatial points to be analyzed for the maximum x value.

Example In this example, the ST_XMAX function returns 2 because it is the largest x value of the specified points.

SQL

SELECT ST_XMAX(
        ST_POLYGON(ST_LINESTRING('LINESTRING(2 5, 1 2, 1 4, 0 3)')));

Output: 2

ST_XMIN

Returns the minimum x value of the specified geography. Syntax

SQL

ST_XMIN(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	One or more geospatial points to be analyzed for the minimum x value.

Example In this example, the ST_XMIN function returns 0 because it is the smallest x value of the specified points.

SQL

SELECT ST_XMIN(
        ST_POLYGON(ST_LINESTRING('LINESTRING(2 5, 1 2, 1 4, 0 3)')));

Output: 0

ST_Y

Returns the y value, or latitude, of the specified POINT. The returned value is a DOUBLE type. Syntax

SQL

ST_Y(point)

Argument	Data Type	Description
`point`	`POINT`	A geospatial point to be analyzed for its y value, the latitude.

Example

SQL

SELECT ST_Y(ST_POINT(3, 5));

Output: 5

ST_YMAX

Returns the maximum y value of the specified geography. Syntax

SQL

ST_YMAX(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	One or more geospatial points to be analyzed for the maximum y value.

Example In this example, the ST_YMAX function returns 5 because it is the largest y value of the specified points.

SQL

SELECT ST_YMAX(
        ST_POLYGON(ST_LINESTRING('LINESTRING(2 5, 1 2, 1 4, 0 3)')));

Output: 5

ST_YMIN

Returns the minimum y value of the specified geography. Syntax

SQL

ST_YMIN(geo)

Argument	Data Type	Description
`geo`	`POINT`, `LINESTRING`, `POLYGON`	One or more geospatial points to be analyzed for the minimum y value.

Example In this example, the ST_YMIN function returns 2 because it is the smallest y value of the specified points.

SQL

SELECT ST_YMIN(
        ST_POLYGON(ST_LINESTRING('LINESTRING(2 5, 1 2, 1 4, 0 3)')));

Output: 2 Geospatial Data Types Linestring Constructors Point Constructors Polygon Constructors

​ST_COORDDIM

​ST_DIMENSION

​ST_GEOMETRYTYPE

​ST_ISEMPTY

​ST_MEMSIZE

​ST_NDIMS or ST_NDIMENSION

​ST_NPOINTS or ST_NUMPOINTS

​ST_SRID

​ST_X

​ST_XMAX

​ST_XMIN

​ST_Y

​ST_YMAX

​ST_YMIN

​Related Links

ST_COORDDIM

ST_DIMENSION

ST_GEOMETRYTYPE

ST_ISEMPTY

ST_MEMSIZE

ST_NDIMS or ST_NDIMENSION

ST_NPOINTS or ST_NUMPOINTS

ST_SRID

ST_X

ST_XMAX

ST_XMIN

ST_Y

ST_YMAX

ST_YMIN

Related Links