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.如果任一个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。

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

ST_Distance_Sphere(g1, g2 [, radius])

Returns the mimimum spherical distance between Point or MultiPoint arguments on a sphere, in meters. 返回球体上Point或MultiPoint参数之间的最小球面距离，单位为米。(For general-purpose distance calculations, see the ST_Distance() function.) （有关一般用途的距离计算，请参见ST_distance()函数。）The optional radius argument should be given in meters.可选radius参数应以米为单位。

If both geometry parameters are valid Cartesian Point or MultiPoint values in SRID 0, the return value is shortest distance between the two geometries on a sphere with the provided radius. 如果两个几何体参数在SRID 0中都是有效的笛卡尔Point或MultiPoint值，则返回值是具有给定半径的球体上两个几何体之间的最短距离。If omitted, the default radius is 6,370,986 meters, Point X and Y coordinates are interpreted as longitude and latitude, respectively, in degrees.如果省略，则默认半径为6370986米，点X和Y坐标分别解释为经度和纬度，单位为度。

If both geometry parameters are valid Point or MultiPoint values in a geographic spatial reference system (SRS), the return value is the shortest distance between the two geometries on a sphere with the provided radius. 如果两个几何参数都是地理空间参考系（SRS）中的有效Point或MultiPoint值，则返回值是具有给定半径的球体上两个几何之间的最短距离。If omitted, the default radius is equal to the mean radius, defined as (2a+b)/3, where a is the semi-major axis and b is the semi-minor axis of the SRS.如果省略，默认半径等于平均半径，定义为(2a+b)/3，其中a是SRS的半长轴，b是SRS的半短轴。

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

mysql> SET @pt1 = ST_GeomFromText('POINT(0 0)');
mysql> SET @pt2 = ST_GeomFromText('POINT(180 0)');
mysql> SELECT ST_Distance_Sphere(@pt1, @pt2);
+--------------------------------+
| ST_Distance_Sphere(@pt1, @pt2) |
+--------------------------------+
|             20015042.813723423 |
+--------------------------------+

ST_IsValid(g)

Returns 1 if the argument is geometrically valid, 0 if the argument is not geometrically valid. 如果参数在几何上有效，则返回1；如果参数在几何上无效，则返回0。Geometry validity is defined by the OGC specification.几何有效性由OGC规范定义。

The only valid empty geometry is represented in the form of an empty geometry collection value. 唯一有效的空几何图形以空几何图形集合值的形式表示。ST_IsValid() returns 1 in this case. 在本例中，ST_IsValid()返回1。MySQL does not support GIS EMPTY values such as POINT EMPTY.MySQL不支持诸如POINT EMPTY之类的GISEMPTY值。

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

mysql> SET @ls1 = ST_GeomFromText('LINESTRING(0 0,-0.00 0,0.0 0)');
mysql> SET @ls2 = ST_GeomFromText('LINESTRING(0 0, 1 1)');
mysql> SELECT ST_IsValid(@ls1);
+------------------+
| ST_IsValid(@ls1) |
+------------------+
|                0 |
+------------------+
mysql> SELECT ST_IsValid(@ls2);
+------------------+
| ST_IsValid(@ls2) |
+------------------+
|                1 |
+------------------+

ST_MakeEnvelope(pt1, pt2)

Returns the rectangle that forms the envelope around two points, as a Point, LineString, or Polygon.返回围绕两点形成封套的矩形，如Point、LineString或Polygon。

Calculations are done using the Cartesian coordinate system rather than on a sphere, spheroid, or on earth.计算是使用笛卡尔坐标系，而不是在球体、球体或地球上进行的。

Given two points pt1 and pt2, ST_MakeEnvelope() creates the result geometry on an abstract plane like this:给定两点pt1和pt2，ST_MakeEnvelope()在抽象平面上创建结果几何体，如下所示：

The result geometry has an SRID of 0.结果几何体的SRID为0。

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

mysql> SET @pt1 = ST_GeomFromText('POINT(0 0)');
mysql> SET @pt2 = ST_GeomFromText('POINT(1 1)');
mysql> SELECT ST_AsText(ST_MakeEnvelope(@pt1, @pt2));
+----------------------------------------+
| ST_AsText(ST_MakeEnvelope(@pt1, @pt2)) |
+----------------------------------------+
| POLYGON((0 0,1 0,1 1,0 1,0 0))         |
+----------------------------------------+

ST_Simplify(g, max_distance)

Simplifies a geometry using the Douglas-Peucker algorithm and returns a simplified value of the same type.使用Douglas Peucker算法简化几何体，并返回相同类型的简化值。

The geometry may be any geometry type, although the Douglas-Peucker algorithm may not actually process every type. 几何体可以是任何几何体类型，尽管Douglas-Peucker算法实际上可能不会处理每种类型。A geometry collection is processed by giving its components one by one to the simplification algorithm, and the returned geometries are put into a geometry collection as result.通过将几何集合的各个组成部分逐一交给简化算法，对几何集合进行处理，并将返回的几何集合放入几何集合中。

The max_distance argument is the distance (in units of the input coordinates) of a vertex to other segments to be removed. max_distance参数是顶点到要删除的其他线段的距离（以输入坐标为单位）。Vertices within this distance of the simplified linestring are removed.在简化线串的这个距离内的顶点将被删除。

According to Boost.Geometry, geometries might become invalid as a result of the simplification process, and the process might create self-intersections. 根据Boost.Geometry，由于简化过程，几何可能会变得无效，并且这个过程可能会创建自相交。To check the validity of the result, pass it to ST_IsValid().要检查结果的有效性，请将其传递给ST_IsValid()。

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

mysql> SET @g = ST_GeomFromText('LINESTRING(0 0,0 1,1 1,1 2,2 2,2 3,3 3)');
mysql> SELECT ST_AsText(ST_Simplify(@g, 0.5));
+---------------------------------+
| ST_AsText(ST_Simplify(@g, 0.5)) |
+---------------------------------+
| LINESTRING(0 0,0 1,1 1,2 3,3 3) |
+---------------------------------+
mysql> SELECT ST_AsText(ST_Simplify(@g, 1.0));
+---------------------------------+
| ST_AsText(ST_Simplify(@g, 1.0)) |
+---------------------------------+
| LINESTRING(0 0,3 3)             |
+---------------------------------+

ST_Validate(g)

Validates a geometry according to the OGC specification. 根据OGC规范验证几何体。A geometry can be syntactically well-formed (WKB value plus SRID) but geometrically invalid. 一个几何可以是语法形式良好的（WKB值加SRID），但几何无效。For example, this polygon is geometrically invalid: 例如，此多边形在几何上无效：POLYGON((0 0, 0 0, 0 0, 0 0, 0 0))

ST_Validate() returns the geometry if it is syntactically well-formed and is geometrically valid, NULL if the argument is not syntactically well-formed or is not geometrically valid or is NULL.如果几何体在语法上格式正确且几何性有效，则ST_Validate()返回该几何体；如果参数在语法上格式不正确或几何体无效或为NULL，则返回NULL。

ST_Validate() can be used to filter out invalid geometry data, although at a cost. ST_Validate()可用于过滤无效的几何体数据，但要付出一定代价。For applications that require more precise results not tainted by invalid data, this penalty may be worthwhile.对于需要更精确结果而不受无效数据污染的应用程序，这种惩罚可能是值得的。

If the geometry argument is valid, it is returned as is, except that if an input Polygon or MultiPolygon has clockwise rings, those rings are reversed before checking for validity. 如果几何体参数有效，则返回原样，但如果输入多边形或多边形具有顺时针环，则在检查有效性之前会反转这些环。If the geometry is valid, the value with the reversed rings is returned.如果几何体有效，则返回带反转环的值。

The only valid empty geometry is represented in the form of an empty geometry collection value. 唯一有效的空几何图形以空几何图形集合值的形式表示。ST_Validate() returns it directly without further checks in this case.在本例中，ST_Validate()直接返回它，而无需进一步检查。

As of MySQL 8.0.13, ST_Validate() handles its arguments as described in the introduction to this section, with these exceptions:从MySQL8.0.13开始，ST_Validate()将按照本节简介中所述处理其参数，但有以下例外：

Prior to MySQL 8.0.13, ST_Validate() handles its arguments as described in the introduction to this section, with these exceptions:在MySQL8.0.13之前，ST_Validate()按照本节简介中所述处理其参数，但有以下例外：

mysql> SET @ls1 = ST_GeomFromText('LINESTRING(0 0)');
mysql> SET @ls2 = ST_GeomFromText('LINESTRING(0 0, 1 1)');
mysql> SELECT ST_AsText(ST_Validate(@ls1));
+------------------------------+
| ST_AsText(ST_Validate(@ls1)) |
+------------------------------+
| NULL                         |
+------------------------------+
mysql> SELECT ST_AsText(ST_Validate(@ls2));
+------------------------------+
| ST_AsText(ST_Validate(@ls2)) |
+------------------------------+
| LINESTRING(0 0,1 1)          |
+------------------------------+