Oracle：子选择中的标识符无效

Question

我正在尝试使用子选择从关联表中获取最后一行，但似乎子选择不知道外部查询中涉及的其中一个表，错误位于 kd.KPI_DEF_ID，无效标识符。将其替换为数字使查询有效。

SELECT bp.bp_id,
     kd.kpi_def_id,
     kd.kpi_name,
     ks.kpi_status_now,
     kd.threshold_min_val,
     kd.threshold_max_val,
     kd.threshold_min_alert,
     kd.threshold_max_alert,
     e.event_id,
     e.event_name,
     (SELECT *
      FROM   (SELECT l.log_desc
            FROM   rator_monitoring.alert_logs l
            WHERE  l.kpi_def_id = kd.kpi_def_id
            ORDER  BY TIMESTAMP DESC)
      WHERE  rownum = 1) log_desc
FROM   business_process bp
JOIN   kpi_definition kd
ON     (kd.bp_id = bp.bp_id)
JOIN   rator_monitoring.kpi_status ks
ON     (ks.kpi_def_id = kd.kpi_def_id)
JOIN   event e
ON     (e.event_id = kd.event_id)
WHERE  kd.kpi_active_current = 'Y';

我能做些什么来解决这个问题？

Answer 1

您需要转换 log_desc 标量子查询，以便在顶层完成相关连接。例如，类似：

SELECT ...
       (SELECT max(l.log_desc) keep (dense_rank first order by l.timestamp desc)
        FROM   rator_monitoring.alert_logs l
        WHERE  l.kpi_def_id = kd.kpi_def_id) log_desc
FROM   ...

注意未经测试。

Answer 2

未测试：使用内联视图重组为连接；虽然不确定性能...

SELECT bp.bp_id,
     kd.kpi_def_id,
     kd.kpi_name,
     ks.kpi_status_now,
     kd.threshold_min_val,
     kd.threshold_max_val,
     kd.threshold_min_alert,
     kd.threshold_max_alert,
     e.event_id,
     e.event_name,
     l.log_desc
FROM   business_process bp
JOIN   kpi_definition kd
  ON   kd.bp_id = bp.bp_id
JOIN   rator_monitoring.kpi_status ks
  ON   ks.kpi_def_id = kd.kpi_def_id
JOIN   event e
  ON   e.event_id = kd.event_id
LEFT JOIN (SELECT log_Desc
        FROM rator_monitoring.alert_logs 
        INNER JOIN (SELECT max(timestamp) mts, kpi_def_ID 
                    FROM  rator_monitoring.alert_logs 
                    GROUP BY kpi_def_ID) Z
          ON Z.mts = l.timestamp
         AND Z.kpi_def_ID = l.kpi_def_ID) l
  ON l.kpi_def_id = kd.kpi_def_id
WHERE  kd.kpi_active_current = 'Y';