从 MemSQL 中的插入值自动计算 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 多边形执行相同的操作？我尝试了几种变体，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没有扩展，因此导致 NULL 区域，但我似乎无法以与 GEOGRAPHY_AREA 相同的方式为 GEOGRAPHY_AREA 创建有效表达式=17=].

编辑： 我能够通过 Joseph Victor 提供的提示解决问题。 A GEOGRAPHY 可以在插入时有效地计算如下：

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，这种很糟糕，但是 lat1 东西在一个字符串中。此外，GEOAGRAPHY_AREA returns 是双精度数，而不是 GEOGRAPHY。尝试

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

从 MemSQL 中的插入值自动计算 GEOGRAPHY 多边形

Automatically compute GEOGRAPHY polygon from inserted values in MemSQL

geospatial

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