ST_Envelope(g)

ST_StartPoint(ls)

ST_EndPoint(ls)

ST_PointN(ls, N)

ST_ExteriorRing(poly)

ST_InteriorRingN(poly, N)

ST_GeometryN(gc, N)

If any argument is NULL, the return value is NULL.如果任何参数为NULL，则返回值为NULL。

If any geometry argument is not a syntactically well-formed geometry, an ER_GIS_INVALID_DATA error occurs.如果任何几何参数不是语法格式良好的几何体，则会发生ER_GIS_INVALID_DATA错误。

If any geometry argument is a syntactically well-formed geometry in an undefined spatial reference system (SRS), an ER_SRS_NOT_FOUND error occurs.如果任何几何参数是未定义空间参考系（SRS)中语法结构良好的几何体，则会发生ER_SRS_NOT_FOUND错误。

For functions that take multiple geometry arguments, if those arguments are not in the same SRS, an ER_GIS_DIFFERENT_SRIDS error occurs.对于采用多个几何参数的函数，如果这些参数不在同一SRS中，则会发生ER_GIS_DIFFERENT_SRIDS错误。

If any geometry argument has an SRID value for a geographic SRS and the function does not handle geographic geometries, an ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS error occurs.如果任何geometry参数具有地理SRS的SRID值，并且函数不处理地理几何体，则会发生ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS错误。

For geographic SRS geometry arguments, if any argument has a longitude or latitude that is out of range, an error occurs:对于地理SRS几何参数，如果任何参数的经度或纬度超出范围，则会发生错误：

Ranges shown are in degrees. 显示的范围以度为单位。If an SRS uses another unit, the range uses the corresponding values in its unit. 如果SRS使用另一个单位，则范围使用其单位中的相应值。The exact range limits deviate slightly due to floating-point arithmetic.由于采用浮点运算，精确的范围限制略有偏差。

Otherwise, the return value is non-NULL.否则，返回值为非NULL。

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

Returns a geometry that represents all points whose distance from the geometry value g is less than or equal to a distance of d. 返回一个几何体，它表示与几何体值g的距离小于或等于d的所有点。The result is in the same SRS as the geometry argument.结果与geometry参数的SRS相同。

If the geometry argument is empty, ST_Buffer() returns an empty geometry.如果几何体参数为空，则ST_Buffer()返回一个空的几何体。

If the distance is 0, ST_Buffer() returns the geometry argument unchanged:如果距离为0，则ST_Buffer()原封不动地返回几何体参数：

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)                   |
+------------------------------+

If the geometry argument is in a Cartesian SRS:如果几何参数在笛卡尔坐标系中：

If the geometry argument is in a geographic SRS:如果几何体参数位于地理区域中：

For MySQL versions that permit geographic Point geometries:对于允许地理Point几何图形的MySQL版本：

ST_Buffer() permits up to three optional strategy arguments following the distance argument. ST_Buffer()允许在距离参数之后最多有三个可选策略参数。Strategies influence buffer computation. 策略影响缓冲区计算。These arguments are byte string values produced by the ST_Buffer_Strategy() function, to be used for point, join, and end strategies:这些参数是由ST_Buffer_Strategy()函数生成的字节字符串值，用于点、连接和末端策略：

Up to one strategy of each type may be specified, and they may be given in any order.每种类型最多可以指定一种策略，并且可以按任意顺序给出。

If the buffer strategies are invalid, an ER_WRONG_ARGUMENTS error occurs. 如果缓冲区策略无效，则会发生ER_WRONG_ARGUMENTS错误。Strategies are invalid under any of these circumstances:在下列任何情况下，策略都是无效的：

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_Strategy(strategy [, points_per_circle])

This function returns a strategy byte string for use with ST_Buffer() to influence buffer computation.此函数返回一个策略字节字符串，与ST_Buffer()一起使用以影响缓冲区计算。

Information about strategies is available at Boost.org.有关战略的信息，请访问Boost.org。

The first argument must be a string indicating a strategy option:第一个参数必须是表示策略选项的字符串：

If the first argument is 'point_circle', 'join_round', 'join_miter', or 'end_round', the points_per_circle argument must be given as a positive numeric value. 如果第一个参数是'point_circle'、'join_round'、'join_miter'或'end_round'，则必须将points_per_circle参数指定为正数值。The maximum points_per_circle value is the value of the max_points_in_geometry system variable.points_per_circle值是max_points_in_geometry系统变量的值。

For examples, see the description of ST_Buffer().有关示例，请参见ST_Buffer()的说明。

ST_Buffer_Strategy() handles its arguments as described in the introduction to this section, with these exceptions:ST_Buffer_Strategy()按本节简介中所述处理其参数，但有以下例外：

ST_ConvexHull(g)

Returns a geometry that represents the convex hull of the geometry value g.返回表示几何体值g的凸包的几何体。

This function computes a geometry's convex hull by first checking whether its vertex points are colinear. 此函数通过首先检查几何体的顶点是否共线来计算几何体的凸包。The function returns a linear hull if so, a polygon hull otherwise. 该函数返回线性外壳（如果是），否则返回多边形外壳。This function processes geometry collections by extracting all vertex points of all components of the collection, creating a MultiPoint value from them, and computing its convex hull.此函数通过提取集合所有组件的所有顶点、从中创建MultiPoint值并计算其凸包来处理几何体集合。

ST_ConvexHull() handles its arguments as described in the introduction to this section, with this exception:ST_ConvexHull()按本节简介中所述处理其参数，但有以下例外：

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_Difference(g1, g2)

Returns a geometry that represents the point set difference of the geometry values g1 and g2. 返回表示几何图形值g1和g2的点集差的几何图形。The result is in the same SRS as the geometry arguments.结果与几何参数的SRS相同。

As of MySQL 8.0.26, ST_Difference() permits arguments in either a Cartesian or a geographic SRS. 从MySQL 8.0.26开始，ST_Difference()允许使用笛卡尔或地理坐标系中的参数。Prior to MySQL 8.0.26, ST_Difference() permits arguments in a Cartesian SRS only; for arguments in a geographic SRS, an ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS error occurs.在MySQL8.0.26之前，ST_Difference()只允许笛卡尔SRS中的参数；对于地理SRS中的参数，会发生ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS错误。

ST_Difference() handles its arguments as described in the introduction to this section.ST_Difference()处理其参数，如本节简介中所述。

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 values g1 and g2. 返回表示几何图形值g1和g2的点集交点的几何图形。The result is in the same SRS as the geometry arguments.结果与几何参数的SRS相同。

As of MySQL 8.0.27, ST_Intersection() permits arguments in either a Cartesian or a geographic SRS. 从MySQL 8.0.27开始，ST_Intersection()允许使用笛卡尔或地理坐标系中的参数。Prior to MySQL 8.0.27, ST_Intersection() permits arguments in a Cartesian SRS only; for arguments in a geographic SRS, an ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS error occurs.在MySQL8.0.27之前，ST_Intersection()只允许笛卡尔SRS中的参数；对于地理SRS中的参数，会发生ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS错误。

ST_Intersection() handles its arguments as described in the introduction to this section.ST_Intersection()处理其参数，如本节简介中所述。

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_LineInterpolatePoint(ls, fractional_distance)

This function takes a LineString geometry and a fractional distance in the range [0.0, 1.0] and returns the Point along the LineString at the given fraction of the distance from its start point to its endpoint. 此函数用于获取LineString几何体和[0.0,1.0]范围内的分数距离，并返回线串上从起点到终点距离的给定分数处的点。It can be used to answer questions such as which Point lies halfway along the road described by the geometry argument.它可以用来回答诸如哪一个Point位于几何体参数所描述的道路的中间等问题。

The function is implemented for LineString geometries in all spatial reference systems, both Cartesian and geographic.该函数用于所有空间参考系（包括笛卡尔坐标系和地理坐标系）中的LineString几何体。

If the fractional_distance argument is 1.0, the result may not be exactly the last point of the LineString argument but a point close to it due to numerical inaccuracies in approximate-value computations.如果fractional_distance参数为1.0，则由于近似值计算中的数值不准确，结果可能不是LineString参数的最后一个点，而是接近它的点。

A related function, ST_LineInterpolatePoints(), takes similar arguments but returns a MultiPoint consisting of Point values along the LineString at each fraction of the distance from its start point to its endpoint. 一个相关的函数，ST_LineInterpolatePoints()，接受类似的参数，但返回一个多点，该多点由从起点到终点的距离的每一个分数处的线串上的点值组成。For examples of both functions, see the ST_LineInterpolatePoints() description.有关这两个函数的示例，请参见ST_LineInterpolatePoints()说明。

ST_LineInterpolatePoint() handles its arguments as described in the introduction to this section, with these exceptions:ST_LineInterpolatePoint()按照本节简介中所述处理其参数，但有以下例外：

ST_LineInterpolatePoint() is a MySQL extension to OpenGIS. ST_LineInterpolatePoint()是OpenGIS的MySQL扩展。This function was added in MySQL 8.0.24.MySQL 8.0.24中增加了这个函数。

ST_LineInterpolatePoints(ls, fractional_distance)

This function takes a LineString geometry and a fractional distance in the range (0.0, 1.0] and returns the MultiPoint consisting of the LineString start point, plus Point values along the LineString at each fraction of the distance from its start point to its endpoint. 此函数获取范围(0.0,1.0)内的LineString几何图形和分数距离，并返回由LineString起点组成的MultiPoint，以及从LineString起点到LineString终点的每一分数处沿LineString的Point值。It can be used to answer questions such as which Point values lie every 10% of the way along the road described by the geometry argument.它可以用来回答一些问题，比如几何参数描述的道路沿线每10%就有哪些Point值。

The function is implemented for LineString geometries in all spatial reference systems, both Cartesian and geographic.该函数用于所有空间参考系（包括笛卡尔坐标系和地理坐标系）中的线串几何图形。

If the fractional_distance argument divides 1.0 with zero remainder the result may not contain the last point of the LineString argument but a point close to it due to numerical inaccuracies in approximate-value computations.如果fractional_distance参数除以1.0，余数为零，则结果可能不包含LineString参数的最后一点，而是由于近似值计算中的数值不准确而接近它的一点。

A related function, ST_LineInterpolatePoint(), takes similar arguments but returns the Point along the LineString at the given fraction of the distance from its start point to its endpoint.一个相关的函数，ST_LineInterpolatePoint()，接受类似的参数，但返回从起点到终点的距离的给定分数处的LineString的Point。

ST_LineInterpolatePoints() handles its arguments as described in the introduction to this section, with these exceptions:ST_LineInterpolatePoints()处理其参数，如本节简介中所述，但有以下例外：

mysql> SET @ls1 = ST_GeomFromText('LINESTRING(0 0,0 5,5 5)');
mysql> SELECT ST_AsText(ST_LineInterpolatePoint(@ls1, .5));
+----------------------------------------------+
| ST_AsText(ST_LineInterpolatePoint(@ls1, .5)) |
+----------------------------------------------+
| POINT(0 5)                                   |
+----------------------------------------------+
mysql> SELECT ST_AsText(ST_LineInterpolatePoint(@ls1, .75));
+-----------------------------------------------+
| ST_AsText(ST_LineInterpolatePoint(@ls1, .75)) |
+-----------------------------------------------+
| POINT(2.5 5)                                  |
+-----------------------------------------------+
mysql> SELECT ST_AsText(ST_LineInterpolatePoint(@ls1, 1));
+---------------------------------------------+
| ST_AsText(ST_LineInterpolatePoint(@ls1, 1)) |
+---------------------------------------------+
| POINT(5 5)                                  |
+---------------------------------------------+
mysql> SELECT ST_AsText(ST_LineInterpolatePoints(@ls1, .25));
+------------------------------------------------+
| ST_AsText(ST_LineInterpolatePoints(@ls1, .25)) |
+------------------------------------------------+
| MULTIPOINT((0 2.5),(0 5),(2.5 5),(5 5))        |
+------------------------------------------------+

ST_LineInterpolatePoints() is a MySQL extension to OpenGIS. ST_LineInterpolatePoints()是OpenGIS的MySQL扩展。This function was added in MySQL 8.0.24.MySQL 8.0.24中增加了这个函数。

ST_PointAtDistance(ls, distance)

This function takes a LineString geometry and a distance in the range [0.0, ST_Length(ls)] measured in the unit of the spatial reference system (SRS) of the LineString, and returns the Point along the LineString at that distance from its start point. 此函数获LineString的几何体和范围[0.0,ST_Length(ls)]内的距离（以线串的空间参考系（SRS）为单位），并返回线串上距离其起点的点。It can be used to answer questions such as which Point value is 400 meters from the start of the road described by the geometry argument.它可以用来回答一些问题，例如哪个Point值是从几何参数描述的道路起点算起的400米。

The function is implemented for LineString geometries in all spatial reference systems, both Cartesian and geographic.该函数用于所有空间参考系（包括笛卡尔坐标系和地理坐标系）中的LineString几何体。

ST_PointAtDistance() handles its arguments as described in the introduction to this section, with these exceptions:ST_PointAtDistance()按本节简介中所述处理其参数，但有以下例外：

ST_PointAtDistance() is a MySQL extension to OpenGIS. ST_PointAtDistance()是OpenGIS的MySQL扩展。This function was added in MySQL 8.0.24.MySQL 8.0.24中增加了这个函数。

ST_SymDifference(g1, g2)

Returns a geometry that represents the point set symmetric difference of the geometry values g1 and g2, which is defined as:返回表示几何图形值g1和g2的点集对称差的几何图形，定义为：

g1 symdifference g2 := (g1 union g2) difference (g1 intersection g2)

Or, in function call notation:或者，在函数调用表示法中：

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

ST_SymDifference() handles its arguments as described in the introduction to this section.ST_SymDifference()处理其参数，如本节简介中所述。

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

ST_Transform(g, target_srid)

Transforms a geometry from one spatial reference system (SRS) to another. 将几何体从一个空间参照系（SRS）变换到另一个空间参照系。The return value is a geometry of the same type as the input geometry with all coordinates transformed to the target SRID, target_srid. 返回值是与输入几何体类型相同的几何体，所有坐标都转换为目标SRIDtarget_srid。Transformation support is limited to geographic SRSs, unless the SRID of the geometry argument is the same as the target SRID value, in which case the return value is the input geometry for any valid SRS.转换支持仅限于地理SRS，除非geometry参数的SRID与目标SRID值相同，在这种情况下，返回值是任何有效SRS的输入几何体。

ST_Transform() handles its arguments as described in the introduction to this section, with these exceptions:ST_Transform()按本节简介中所述处理其参数，但有以下例外：

ST_SRID(g, target_srid) and ST_Transform(g, target_srid) differ as follows:

mysql> SET @p = ST_GeomFromText('POINT(52.381389 13.064444)', 4326);
mysql> SELECT ST_AsText(@p);
+----------------------------+
| ST_AsText(@p)              |
+----------------------------+
| POINT(52.381389 13.064444) |
+----------------------------+
mysql> SET @p = ST_Transform(@p, 4230);
mysql> SELECT ST_AsText(@p);
+---------------------------------------------+
| ST_AsText(@p)                               |
+---------------------------------------------+
| POINT(52.38208611407426 13.065520672345304) |
+---------------------------------------------+

ST_Union(g1, g2)

Returns a geometry that represents the point set union of the geometry values g1 and g2. 返回表示几何图形值g1和g2的点集并集的几何图形。The result is in the same SRS as the geometry arguments.结果与几何参数的SRS相同。

As of MySQL 8.0.26, ST_Union() permits arguments in either a Cartesian or a geographic SRS. 从MySQL 8.0.26开始，ST_Union()允许使用笛卡尔或地理形式的参数。Prior to MySQL 8.0.26, ST_Union() permits arguments in a Cartesian SRS only; for arguments in a geographic SRS, an ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS error occurs.在MySQL8.0.26之前，ST_Union()只允许笛卡尔SRS中的参数；对于地理SRS中的参数，会发生ER_NOT_IMPLEMENTED_FOR_GEOGRAPHIC_SRS错误。

ST_Union() handles its arguments as described in the introduction to this section.ST_Union()处理其参数，如本节简介中所述。

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)) |
+--------------------------------------+