DOUBLE ST_Y(POINT point)
当point是一个合法的POINT类型时,返回对应的Y坐标值
MySQL > SELECT ST_Y(ST_Point(24.7, 56.7));
+----------------------------+
| st_y(st_point(24.7, 56.7)) |
+----------------------------+
| 56.7 |
+----------------------------+
ST_Y,ST,Y