MySQL offers `ENVELOPE()`

to find the minimum bounding rectangle of a geometric object.

The result is a polygon with four segments, defined by five points. It took me a while to make sense of it, partially because the only documentation that I’ve run across so far for `POLYGON()`

syntax is in the `ENVELOPE()`

function mentioned above. I also had to draw a picture to think it through.

They write this: `POLYGON(( MINX MINY, MAXX MINY, MAXX MAXY, MINX MAXY, MINX MINY ))`

, I think this (in pseudocode-ish form): `POLYGON(( $point_a, $point_b, $point_c, $point_d, $point_a ))`

, with the `$point_`

s corresponding to the diagram.