DB2 Version 9.7 for Linux, UNIX, and Windows

Well-known text (WKT) representation

The OpenGIS Consortium "Simple Features for SQL" specification defines the well-known text representation to exchange geometry data in ASCII format. This representation is also referenced by the ISO "SQL/MM Part: 3 Spatial" standard. See "Spatial functions that convert geometries to and from data exchange formats" for information on functions which accept and produce WKT data.

The well-known text representation of a geometry is defined as follows:


>>-+-POINT-----------+--+-| point-tagged-text |-----------+----><
   +-LINESTRING------+  +-| linestring-tagged text |------+   
   +-POLYGON---------+  +-| polygon-tagged-text |---------+   
   +-MULTIPOINT------+  +-| multipoint-tagged-text |------+   
   +-MULTILINESTRING-+  +-| multilinestring-tagged-text |-+   
   '-MULTIPOLYGON----'  '-| multipolygon-tagged-text |----'   

point-tagged-text

|--+--+-EMPTY-----------------------+------+--------------------|
   |  '-(--| point-coordinates |--)-'      |   
   +-Z-+-EMPTY-------------------------+---+   
   |   '-(--| point-z-coordinates |--)-'   |   
   +-M-+-EMPTY-------------------------+---+   
   |   '-(--| point-m-coordinates |--)-'   |   
   '-ZM-+-EMPTY--------------------------+-'   
        '-(--| point-zm-coordinates |--)-'     

linestring-tagged-text

|--+--+-EMPTY-----------------------+------+--------------------|
   |  '-(--| linestring-points |--)-'      |   
   +-Z-+-EMPTY-------------------------+---+   
   |   '-(--| linestring-z-points |--)-'   |   
   +-M-+-EMPTY-------------------------+---+   
   |   '-(--| linestring-m-points |--)-'   |   
   '-ZM-+-EMPTY--------------------------+-'   
        '-(--| linestring-zm-points |--)-'     

polygon-tagged-text

|--+--+-EMPTY-------------------+------+------------------------|
   |  '-(--| polygon-rings |--)-'      |   
   +-Z-+-EMPTY---------------------+---+   
   |   '-(--| polygon-z-rings |--)-'   |   
   +-M-+-EMPTY---------------------+---+   
   |   '-(--| polygon-m-rings |--)-'   |   
   '-ZM-+-EMPTY----------------------+-'   
        '-(--| polygon-zm-rings |--)-'     

multipoint-tagged-text

|--+--+-EMPTY----------------------+------+---------------------|
   |  '-(--| multipoint-parts |--)-'      |   
   +-Z-+-EMPTY------------------------+---+   
   |   '-(--| multipoint-z-parts |--)-'   |   
   +-M-+-EMPTY------------------------+---+   
   |   '-(--| multipoint-m-parts |--)-'   |   
   '-ZM-+-EMPTY-------------------------+-'   
        '-(--| multipoint-zm-parts |--)-'     

multilinestring-tagged-text

|--+--+-EMPTY---------------------------+------+----------------|
   |  '-(--| multilinestring-parts |--)-'      |   
   +-Z-+-EMPTY-----------------------------+---+   
   |   '-(--| multilinestring-z-parts |--)-'   |   
   +-M-+-EMPTY-----------------------------+---+   
   |   '-(--| multilinestring-m-parts |--)-'   |   
   '-ZM-+-EMPTY------------------------------+-'   
        '-(--| multilinestring-zm-parts |--)-'     

multipolygon-tagged-text

|--+--+-EMPTY------------------------+------+-------------------|
   |  '-(--| multipolygon-parts |--)-'      |   
   +-Z-+-EMPTY--------------------------+---+   
   |   '-(--| multipolygon-z-parts |--)-'   |   
   +-M-+-EMPTY--------------------------+---+   
   |   '-(--| multipolygon-m-parts |--)-'   |   
   '-ZM-+-EMPTY---------------------------+-'   
        '-(--| multipolygon-zm-parts |--)-'     

point-coordinates

|--x_coord--y_coord---------------------------------------------|

point-z-coordinates

|--| point-coordinates |--y_coord-------------------------------|

point-m-coordinates

|--| point-coordinates |--m_coord-------------------------------|

point-zm-coordinates

|--| point-coordinates |--y_coord--m_coord----------------------|


linestring-points

                               .-,-----------------------.   
                               V                         |   
|----| point-coordinates |--,----| point-coordinates |---+------|

linestring-z-points

|----| point-z-coordinates |--,--------------------------------->

   .-,-------------------------.   
   V                           |   
>----| point-z-coordinates |---+--------------------------------|

linestring-m-points

|----| point-m-coordinates |--,--------------------------------->

   .-,-------------------------.   
   V                           |   
>----| point-m-coordinates |---+--------------------------------|

linestring-zm-points

|----| point-zm-coordinates |--,-------------------------------->

   .-,--------------------------.   
   V                            |   
>----| point-zm-coordinates |---+-------------------------------|

polygon-rings

   .-,--------------------------------------------------.   
   V                                                    |   
|----(--| linestring-points |--| linestring-points |--)-+-------|

polygon-z-rings

   .-,------------------------------------------------------.   
   V                                                        |   
|----(--| linestring-z-points |--| linestring-z-points |--)-+---|

polygon-m-rings

   .-,------------------------------------------------------.   
   V                                                        |   
|----(--| linestring-m-points |--| linestring-m-points |--)-+---|

polygon-zm-rings

   .-,--------------------------------------------------------.   
   V                                                          |   
|----(--| linestring-zm-points |--| linestring-zm-points |--)-+--|

multipoint-parts

   .-,-------------------------.   
   V                           |   
|------| point-coordinates |---+--------------------------------|

multipoint-z-parts

   .-,---------------------------.   
   V                             |   
|------| point-z-coordinates |---+------------------------------|

multipoint-m-parts

   .-,---------------------------.   
   V                             |   
|------| point-m-coordinates |---+------------------------------|

multipoint-zm-parts

   .-,----------------------------.   
   V                              |   
|------| point-zm-coordinates |---+-----------------------------|

multilinestring-parts

   .-,---------------------------.   
   V                             |   
|----(--| linestring-points |--)-+------------------------------|

multilinestring-z-parts

   .-,-----------------------------.   
   V                               |   
|----(--| linestring-z-points |--)-+----------------------------|

multilinestring-m-parts

   .-,-----------------------------.   
   V                               |   
|----(--| linestring-m-points |--)-+----------------------------|

multilinestring-zm-parts

   .-,------------------------------.   
   V                                |   
|----(--| linestring-zm-points |--)-+---------------------------|

multipolygon-parts

   .-,-----------------------.   
   V                         |   
|----(--| polygon-rings |--)-+----------------------------------|

multipolygon-z-parts

   .-,-------------------------.   
   V                           |   
|----(--| polygon-z-rings |--)-+--------------------------------|

multipolygon-m-parts

   .-,-------------------------.   
   V                           |   
|----(--| polygon-m-rings |--)-+--------------------------------|

multipolygon-zm-parts

   .-,--------------------------.   
   V                            |   
|----(--| polygon-zm-rings |--)-+-------------------------------|

Parameters

x_coord

A numerical value (fixed, integer, or floating point), which represents the X coordinate of a point.

y_coord

A numerical value (fixed, integer, or floating point), which represents the Y coordinate of a point.

z_coord

A numerical value (fixed, integer, or floating point), which represents the Z coordinate of a point.

m_coord

A numerical value (fixed, integer, or floating point), which represents the M coordinate (measure) of a point.

If the geometry is empty, then the keyword EMPTY is to be specified instead of the coordinate list. The EMPTY keyword must not be embedded within the coordinate list

The following table provides some examples of possible text representations.

Table 1. Geometry types and their text representations
Geometry type	WKT representation	Comment
point	POINT EMPTY	empty point
point	POINT ( 10.05 10.28 )	point
point	POINT Z( 10.05 10.28 2.51 )	point with Z coordinate
point	POINT M( 10.05 10.28 4.72 )	point with M coordinate
point	POINT ZM( 10.05 10.28 2.51 4.72 )	point with Z coordinate and M coordinate
linestring	LINESTRING EMPTY	empty linestring
polygon	POLYGON (( 10 10, 10 20, 20 20, 20 15, 10 10))	polygon
multipoint	MULTIPOINT Z(10 10 2, 20 20 3)	multipoint with Z coordinates
multilinestring	MULTILINESTRING M(( 310 30 1, 40 30 20, 50 20 10 )( 10 10 0, 20 20 1))	multilinestring with M coordinates
multipolygon	MULTIPOLYGON ZM((( 1 1 1 1, 1 2 3 4, 2 2 5 6, 2 1 7 8, 1 1 1 1 )))	multipolygon with Z coordinates and M coordinates