Movatterモバイル変換

ST_Envelope(g)

ST_StartPoint(ls)

ST_EndPoint(ls)

ST_PointN(ls,N)

ST_ExteriorRing(poly)

ST_InteriorRingN(poly,N)

ST_GeometryN(gc,N)

Buffer(g,d [,strategy1 [,strategy2 [,strategy3]]])

ST_Buffer() andBuffer() are synonyms. For more information, see the description ofST_Buffer().

Buffer() is deprecated; expect it to be removed in a future MySQL release. UseST_Buffer() instead.

ConvexHull(g)

ST_ConvexHull() andConvexHull() are synonyms. For more information, see the description ofST_ConvexHull().

ConvexHull() is deprecated; expect it to be removed in a future MySQL release. UseST_ConvexHull() instead.

ST_Buffer(g,d [,strategy1 [,strategy2 [,strategy3]]])

Returns a geometry that represents all points whose distance from the geometry valueg is less than or equal to a distance ofd, orNULL if any argument isNULL. The SRID of the geometry argument must be 0 becauseST_Buffer() supports only the Cartesian coordinate system. If any geometry argument is not a syntactically well-formed geometry, anER_GIS_INVALID_DATA error occurs.

If the geometry argument is empty,ST_Buffer() returns an empty geometry.

If the distance is 0,ST_Buffer() returns the geometry argument unchanged:

mysql> SET @pt = ST_GeomFromText('POINT(0 0)');mysql> SELECT ST_AsText(ST_Buffer(@pt, 0));+------------------------------+| ST_AsText(ST_Buffer(@pt, 0)) |+------------------------------+| POINT(0 0)                   |+------------------------------+

ST_Buffer() supports negative distances forPolygon andMultiPolygon values, and for geometry collections containingPolygon orMultiPolygon values. The result may be an empty geometry. AnER_WRONG_ARGUMENTS error occurs forST_Buffer() with a negative distance forPoint,MultiPoint,LineString, andMultiLineString values, and for geometry collections not containing anyPolygon orMultiPolygon values.

ST_Buffer() permits up to three optional strategy arguments following the distance argument. Strategies influence buffer computation. These arguments are byte string values produced by theST_Buffer_Strategy() function, to be used for point, join, and end strategies:

Up to one strategy of each type may be specified, and they may be given in any order. If multiple strategies of a given type are specified, anER_WRONG_ARGUMENTS error occurs.

mysql> SET @pt = ST_GeomFromText('POINT(0 0)');mysql> SET @pt_strategy = ST_Buffer_Strategy('point_square');mysql> SELECT ST_AsText(ST_Buffer(@pt, 2, @pt_strategy));+--------------------------------------------+| ST_AsText(ST_Buffer(@pt, 2, @pt_strategy)) |+--------------------------------------------+| POLYGON((-2 -2,2 -2,2 2,-2 2,-2 -2))       |+--------------------------------------------+

mysql> SET @ls = ST_GeomFromText('LINESTRING(0 0,0 5,5 5)');mysql> SET @end_strategy = ST_Buffer_Strategy('end_flat');mysql> SET @join_strategy = ST_Buffer_Strategy('join_round', 10);mysql> SELECT ST_AsText(ST_Buffer(@ls, 5, @end_strategy, @join_strategy))+---------------------------------------------------------------+| ST_AsText(ST_Buffer(@ls, 5, @end_strategy, @join_strategy))   |+---------------------------------------------------------------+| POLYGON((5 5,5 10,0 10,-3.5355339059327373 8.535533905932738, || -5 5,-5 0,0 0,5 0,5 5))                                       |+---------------------------------------------------------------+

ST_Buffer() andBuffer() are synonyms.

ST_Buffer_Strategy(strategy [,points_per_circle])

This function returns a strategy byte string for use withST_Buffer() to influence buffer computation. If any argument isNULL, the return value isNULL. If any argument is invalid, anER_WRONG_ARGUMENTS error occurs.

Information about strategies is available atBoost.org.

The first argument must be a string indicating a strategy option:

If the first argument is'point_circle','join_round','join_miter', or'end_round', thepoints_per_circle argument must be given as a positive numeric value. The maximumpoints_per_circle value is the value of themax_points_in_geometry system variable. If the first argument is'point_square' or'end_flat', thepoints_per_circle argument must not be given or anER_WRONG_ARGUMENTS error occurs.

For examples, see the description ofST_Buffer().

ST_ConvexHull(g)

Returns a geometry that represents the convex hull of the geometry valueg. If the argument isNULL, the return value isNULL.

This function computes a geometry's convex hull by first checking whether its vertex points are colinear. The function returns a linear hull if so, a polygon hull otherwise. This function processes geometry collections by extracting all vertex points of all components of the collection, creating aMultiPoint value from them, and computing its convex hull. If the argument is an empty geometry collection, the return value isNULL.

mysql> SET @g = 'MULTIPOINT(5 0,25 0,15 10,15 25)';mysql> SELECT ST_AsText(ST_ConvexHull(ST_GeomFromText(@g)));+-----------------------------------------------+| ST_AsText(ST_ConvexHull(ST_GeomFromText(@g))) |+-----------------------------------------------+| POLYGON((5 0,25 0,15 25,5 0))                 |+-----------------------------------------------+

ST_ConvexHull() andConvexHull() are synonyms.

ST_Difference(g1,g2)

Returns a geometry that represents the point set difference of the geometry valuesg1 andg2. If any argument isNULL, the return value isNULL.

mysql> SET @g1 = Point(1,1), @g2 = Point(2,2);mysql> SELECT ST_AsText(ST_Difference(@g1, @g2));+------------------------------------+| ST_AsText(ST_Difference(@g1, @g2)) |+------------------------------------+| POINT(1 1)                         |+------------------------------------+

ST_Intersection(g1,g2)

Returns a geometry that represents the point set intersection of the geometry valuesg1 andg2. If any argument isNULL, the return value isNULL.

mysql> SET @g1 = ST_GeomFromText('LineString(1 1, 3 3)');mysql> SET @g2 = ST_GeomFromText('LineString(1 3, 3 1)');mysql> SELECT ST_AsText(ST_Intersection(@g1, @g2));+--------------------------------------+| ST_AsText(ST_Intersection(@g1, @g2)) |+--------------------------------------+| POINT(2 2)                           |+--------------------------------------+

ST_SymDifference(g1,g2)

Returns a geometry that represents the point set symmetric difference of the geometry valuesg1 andg2, which is defined as:

g1 symdifferenceg2 := (g1 uniong2) difference (g1 intersectiong2)

Or, in function call notation:

ST_SymDifference(g1,g2) = ST_Difference(ST_Union(g1,g2), ST_Intersection(g1,g2))

If any argument isNULL, the return value isNULL.

mysql> SET @g1 = ST_GeomFromText('MULTIPOINT(5 0,15 10,15 25)');mysql> SET @g2 = ST_GeomFromText('MULTIPOINT(1 1,15 10,15 25)');mysql> SELECT ST_AsText(ST_SymDifference(@g1, @g2));+---------------------------------------+| ST_AsText(ST_SymDifference(@g1, @g2)) |+---------------------------------------+| MULTIPOINT((1 1),(5 0))               |+---------------------------------------+

ST_Union(g1,g2)

Returns a geometry that represents the point set union of the geometry valuesg1 andg2. If any argument isNULL, the return value isNULL.

mysql> SET @g1 = ST_GeomFromText('LineString(1 1, 3 3)');mysql> SET @g2 = ST_GeomFromText('LineString(1 3, 3 1)');mysql> SELECT ST_AsText(ST_Union(@g1, @g2));+--------------------------------------+| ST_AsText(ST_Union(@g1, @g2))        |+--------------------------------------+| MULTILINESTRING((1 1,3 3),(1 3,3 1)) |+--------------------------------------+