SQL Reference
Geospatial Functions

Attribute Functions

 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


Parameter

Data Type

Description

geo

POINT, LINESTRING, or POLYGON

The geospatial object used to calculate the dimensions.

Example

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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


Parameter

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.

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Output: -1

In this example, the function evaluates a LINESTRING with a single POINT value.

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Output: 0

This example evaluates an empty LINESTRING.

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Output: -1

In this example, the function again evaluates a LINESTRING with a single POINT value.

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Output: 0

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

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Output: 1

This example evaluates an empty POLYGON.

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Output: -1

This example evaluates a POLYGON with a single POINT.

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Output: 0

This example evaluates a POLYGON with two POINT values.

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Output: 1

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

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Output: 2

ST_GEOMETRYTYPE

Returns a string representing the geometry type of the input value. Recognized values include ST_POINT, ST_LINESTRING, and ST_POLYGON and NULL.

Syntax

SQL


Parameter

Data Type

Description

geo

POINT, LINESTRING, POLYGON

A geospatial value to be identified by its geometry type.

Example

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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


Parameter

Data Type

Description

geo

POINT, LINESTRING, POLYGON

A geospatial value to be examined if it is empty.

Example

SQL


Output: TRUE

ST_MEMSIZE

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

Syntax

SQL


Parameter

Data Type

Description

geo

POINT, LINESTRING, POLYGON

A geospatial value to be measured by its data memory.

Example

SQL


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

SQL


Parameter

Data Type

Description

geo

POINT, LINESTRING, POLYGON

A geospatial value to be examined for its count of POINT values.

Example

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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


Parameter

Data Type

Description

geo

POINT, LINESTRING, POLYGON

A geospatial value to be analyzed for its EPSG code.

Example

SQL


Output4326

ST_X

Returns the x value of the given POINT. The returned value is a DOUBLE type.

Syntax

SQL


Parameter

Data Type

Description

point

POINT

A geospatial point to be analyzed for its x value.

Example

SQL


Output: 3

ST_XMAX

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

Syntax

SQL


Parameter

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.

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Output: 2

ST_XMIN

Returns the minimum x value of the specified geography.

Syntax

SQL


Parameter

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


Output: 0

ST_Y

Returns the y value of the specified POINT. The returned value is a DOUBLE type.

Syntax

SQL


Parameter

Data Type

Description

point

POINT

A geospatial point to be analyzed for its y value.

Example

SQL


Output: 5

ST_YMAX

Returns the maximum y value of specified geography.

Syntax

SQL


Parameter

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


Output: 5

ST_YMIN

Returns the minimum y value of specified geography.

Syntax

SQL


Parameter

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


Output: 2