geospatial - 根据 MemSQL 中插入的值自动计算 GEOGRAPHY 多边形

Question

在 MemSQL 中，我可以轻松地根据插入的值自动计算 GEOGRAPHYPOINT:

CREATE TABLE point_test (
  id INTEGER NOT NULL,
  lon DECIMAL,
  lat DECIMAL,
  point AS GEOGRAPHY_POINT(lon, lat) PERSISTED GEOGRAPHYPOINT,
  PRIMARY KEY (id)
);

如何对 GEOGRAPHY 多边形执行相同操作？我尝试过几种变体，例如

CREATE TABLE area_test (
  id INTEGER NOT NULL,
  lon1 DECIMAL,
  lon2 DECIMAL,
  lat1 DECIMAL,
  lat2 DECIMAL,
  area AS GEOGRAPHY_AREA("POLYGON((lon1 lat1, lon1 lat2, lon2 lat2, lon2 lat1, lon1 lat1))") PERSISTED GEOGRAPHY,
  PRIMARY KEY (id)
);

但无济于事。我可以看到多边形中的字段在插入期间不会扩展，因此导致 NULL 区域，但我似乎无法为 GEOGRAPHY_AREA 创建有效的表达式与 GEOGRAPHY_POINT 的方式相同。

编辑:我能够根据约瑟夫·维克多提供的提示解决这个问题。 GEOGRAPHY 可以在插入时有效地计算，如下所示:

CREATE TABLE area_test (
 id INTEGER NOT NULL,
 lon1 DECIMAL,
 lon2 DECIMAL,
 lat1 DECIMAL,
 lat2 DECIMAL,
 area AS CONCAT("POLYGON((", lon1," ",lat1,",",lon1," ",lat2,",",lon2," ",lat2,",",lon2," ",lat1,",",lon1," ",lat1,"))") PERSISTED GEOGRAPHY,
 PRIMARY KEY (id)
);

Answer 1

所以，这很糟糕，但是 lat1 的东西在一个字符串中。另外，GEOAGRAPHY_AREA 返回 double 值，而不是 GEOGRAPHY。尝试一下

area AS GEOGRAPHY_AREA(CONCAT("POLYGON((",
                              lon1,
                              " ",
                              lon2,
                              ",",
 ...
                              ")")) PERSISTED DOUBLE