mysql - SQL查询优化/重构

Question

有什么方法可以优化以下查询。

以下查询工作正常，但我多次使用 where 和 from 条件。

查询:

    SELECT st_astext(st_line_substring(
                                     (SELECT st_linemerge(geom)
                                      FROM geom_line
                                      WHERE i_project = $id),
                                     (SELECT $bas/st_length(geom)
                                      FROM geom_line
                                      WHERE i_project = $id),
                                     (SELECT $son/st_length(geom)
                                      FROM geom_line
                                      WHERE i_project = $id) ))
FROM geom_line
WHERE i_project = $id;

问候。 !

Answer 1

我觉得你可以这样试试

SELECT st_astext(st_line_substring(  st_linemerge(geom)  ,
                                  $bas/st_length(geom),
                                 $son/st_length(geom) ))
FROM geom_line
WHERE i_project = $id;