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