openGauss SQL参考—函数和操作符：几何函数和操作符（5）

几何类型转换函数

• box(circle)

  描述：将圆转换成矩形

  返回类型：box

  示例：

  openGauss=# SELECT box(circle '((0,0),2.0)') AS RESULT;
                                    result                                   
  ---------------------------------------------------------------------------
   (1.41421356237309,1.41421356237309),(-1.41421356237309,-1.41421356237309)
  (1 row)
  

• box(point, point)

  描述：将点转换成矩形

  返回类型：box

  示例：

  openGauss=# SELECT box(point '(0,0)', point '(1,1)') AS RESULT;
     result    
  -------------
   (1,1),(0,0)
  (1 row)
  

• box(polygon)

  描述：将多边形转换成矩形

  返回类型：box

  示例：

  openGauss=# SELECT box(polygon '((0,0),(1,1),(2,0))') AS RESULT;
     result    
  -------------
   (2,1),(0,0)
  (1 row)
  

• circle(box)

  描述：矩形转换成圆

  返回类型：circle

  示例：

  openGauss=# SELECT circle(box '((0,0),(1,1))') AS RESULT;
              result             
  -------------------------------
   <(0.5,0.5),0.707106781186548>
  (1 row)
  

• circle(point, double precision)

  描述：将圆心和半径转换成圆

  返回类型：circle

  示例：

  openGauss=# SELECT circle(point '(0,0)', 2.0) AS RESULT;
    result   
  -----------
   <(0,0),2>
  (1 row)
  

• circle(polygon)

  描述：将多边形转换成圆

  返回类型：circle

  示例：

  openGauss=# SELECT circle(polygon '((0,0),(1,1),(2,0))') AS RESULT;
                    result                   
  -------------------------------------------
   <(1,0.333333333333333),0.924950591148529>
  (1 row)
  

• lseg(box)

  描述：矩形对角线转化成线段

  返回类型：lseg

  示例：

  openGauss=# SELECT lseg(box '((-1,0),(1,0))') AS RESULT;
       result     
  ----------------
   [(1,0),(-1,0)]
  (1 row)
  

• lseg(point, point)

  描述：点转换成线段

  返回类型：lseg

  示例：

  openGauss=# SELECT lseg(point '(-1,0)', point '(1,0)') AS RESULT;
       result     
  ----------------
   [(-1,0),(1,0)]
  (1 row)
  

• slope(point, point)

  描述：计算两个点构成直线的斜率

  返回类型: double

  示例：

  openGauss=# SELECT slope(point '(1,1)', point '(0,0)') AS RESULT;
   result
  --------
        1
  (1 row)
  

• path(polygon)

  描述：多边形转换成路径

  返回类型：path

  示例：

  openGauss=# SELECT path(polygon '((0,0),(1,1),(2,0))') AS RESULT;
         result        
  ---------------------
   ((0,0),(1,1),(2,0))
  (1 row)
  

• point(double precision, double precision)

  描述：节点

  返回类型：point

  示例：

  openGauss=# SELECT point(23.4, -44.5) AS RESULT;
      result    
  --------------
   (23.4,-44.5)
  (1 row)
  

• point(box)

  描述：矩形的中心

  返回类型：point

  示例：

  openGauss=# SELECT point(box '((-1,0),(1,0))') AS RESULT;
   result 
  --------
   (0,0)
  (1 row)
  

• point(circle)

  描述：圆心

  返回类型：point

  示例：

  openGauss=# SELECT point(circle '((0,0),2.0)') AS RESULT;
   result 
  --------
   (0,0)
  (1 row)
  

• point(lseg)

  描述：线段的中心

  返回类型：point

  示例：

  openGauss=# SELECT point(lseg '((-1,0),(1,0))') AS RESULT;
   result 
  --------
   (0,0)
  (1 row)
  

• point(polygon)

  描述：多边形的中心

  返回类型：point

  示例：

  openGauss=# SELECT point(polygon '((0,0),(1,1),(2,0))') AS RESULT;
          result         
  -----------------------
   (1,0.333333333333333)
  (1 row)
  

• polygon(box)

  描述：矩形转换成4点多边形

  返回类型：polygon

  示例：

  openGauss=# SELECT polygon(box '((0,0),(1,1))') AS RESULT;
            result           
  ---------------------------
   ((0,0),(0,1),(1,1),(1,0))
  (1 row)
  

• polygon(circle)

  描述：圆转换成12点多边形

  返回类型：polygon

  示例：

  openGauss=# SELECT polygon(circle '((0,0),2.0)') AS RESULT;
                                                                                                                                                  result                                                                                      
  
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   ((-2,0),(-1.73205080756888,1),(-1,1.73205080756888),(-1.22464679914735e-16,2),(1,1.73205080756888),(1.73205080756888,1),(2,2.44929359829471e-16),(1.73205080756888,-0.999999999999999),(1,-1.73205080756888),(3.67394039744206e-16,-2),(-0.999999999999999,-1.73205080756888),(-1.73205080756888,-1))
  (1 row)
  

• polygon(npts, circle)

  描述：圆转换成npts点多边形

  返回类型：polygon

  示例：

  openGauss=# SELECT polygon(12, circle '((0,0),2.0)') AS RESULT;
                                                                                                                                                  result                                                                                      
  
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
   ((-2,0),(-1.73205080756888,1),(-1,1.73205080756888),(-1.22464679914735e-16,2),(1,1.73205080756888),(1.73205080756888,1),(2,2.44929359829471e-16),(1.73205080756888,-0.999999999999999),(1,-1.73205080756888),(3.67394039744206e-16,-2),(-0.999999999999999,-1.73205080756888),(-1.73205080756888,-1))
  (1 row)
  

• polygon(path)

  描述：路径转换成多边形

  返回类型：polygon

  示例：

  openGauss=# SELECT polygon(path '((0,0),(1,1),(2,0))') AS RESULT;
         result        
  ---------------------
   ((0,0),(1,1),(2,0))
  (1 row)