循環中MySQL中兩個POINT值之間的距離

Question

我正在將幾何數據存儲在MySQL數據庫中

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| ID | SPATIAL_INDEX | COORDS         | DISTANCE  |
| 1  | ...           | POINT(0.5,0.5) |     0     |
| 2  | ...           | POINT(0.7,0.7) |     ?     |
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坐標來自2D笛卡爾跟蹤系統。 如何用一行的坐標到最后一行的距離填充DISTANCE列？

Row 1: Distance = 0;
Row 2: Distance = Distance between coords of row 1 and row 2
Row 3: Distance = Distance between coords of row 2 and row 3
[...]

Answer 1

SQL具有特殊的空間功能，可以計算兩點之間的距離。 您可以使用它加上表本身上的聯接來實現所需的功能。

UPDATE tablename AS a 
LEFT JOIN tablename AS b 
ON b.id = a.id-1 
SET a.distance = IFNULL(DISTANCE(a.coord,b.coord),0);