Question

在MemSQL中，我可以轻松地从插入的值中自动计算GEOGRAPHYPOINT：

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

我如何使用GEOGRAPHY多边形做同样的事情？我尝试了几种变体，比如

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展开，因此导致NULL区域，但我似乎无法以与GEOGRAPHY_AREA相同的方式创建GEOGRAPHY_POINT的有效表达式。 GEOGRAPHY。

修改我能够用Joseph Victor提供的提示解决问题。可以在插入上有效地计算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) );，如下所示：

realpath

Answer 1

所以，这种情况很糟糕，但是lat1的东西都在一个字符串中。此外，GEOAGRAPHY_AREA返回双倍，而不是地理。试试

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

从MemSQL中插入的值自动计算GEOGRAPHY多边形

1 个答案: