SELECT r.sonOrgId, o.NAME sonOrgName, ROUND(sum( r.length ) ,3) routeLength, ROUND(sum( rb.length ) ,3) baseRouteLength, IFNULL(sum(g.length),0) length, IFNULL(SUM( gs.saplingNum ),0) saplingNum FROM base_e_route r LEFT JOIN system_organization o ON r.sonOrgId = o.organizationId LEFT JOIN base_e_route_basesection rb ON r.mainRouteId = rb.id LEFT JOIN base_greening g ON g.route_id = r.id LEFT JOIN (SELECT main_id,SUM( sapling_num ) saplingNum from base_greening_son ) gs ON gs.main_id = g.id WHERE o.NAME IS NOT NULL GROUP BY r.sonOrgId ORDER BY o.orderNo统计saplingNum错误

根据你提供的 SQL 语句，我发现在 SELECT 语句中包含了一个子查询，但是这个子查询并没有在 FROM 语句中进行连接。因此，你需要将这个子查询进行连接，可以使用 LEFT JOIN 进行连接。修改后的 SQL 语句如下：

SELECT 
    r.sonOrgId, 
    o.NAME sonOrgName, 
    ROUND(sum(r.length), 3) routeLength, 
    ROUND(sum(rb.length), 3) baseRouteLength, 
    IFNULL(sum(g.length), 0) length, 
    IFNULL(SUM(gs.saplingNum), 0) saplingNum
FROM 
    base_e_route r 
    LEFT JOIN system_organization o ON r.sonOrgId = o.organizationId 
    LEFT JOIN base_e_route_basesection rb ON r.mainRouteId = rb.id 
    LEFT JOIN base_greening g ON g.route_id = r.id 
    LEFT JOIN (
        SELECT main_id, SUM(sapling_num) saplingNum 
        FROM base_greening_son 
        GROUP BY main_id
    ) gs ON gs.main_id = g.id 
WHERE 
    o.NAME IS NOT NULL 
GROUP BY 
    r.sonOrgId 
ORDER BY 
    o.orderNo

注意，这里对子查询进行了修改，对 sapling_num 进行了 SUM 操作，并添加了 GROUP BY 子句。如果还有其他问题，可以再和我讨论哦。