SQL查詢優化/重構

Question

有什么方法可以優化以下查詢。

以下查詢工作正常，但我多次使用where和from條件。

查詢：

    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;

問候。 ！

Answer 1

我想你可以這樣嘗試

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