Oracle - 在删除其他表中的几行之前检查行是否存在

Question

如果主表的 ID 已经存在，我想删除 Oracle 数据库中的几行： 在根据其他表中的 ID 删除行之前，我尝试先进行 SELECT 以检查主表中是否存在该 ID：

DECLARE
    PROJECT_ID PLS_INTEGER;
    PROJECT_ID_TO_DELETE PLS_INTEGER;
BEGIN
    PROJECT_ID := PROJECTS_SEQ.nextval; 
    SELECT PROJ_ID INTO PROJECT_ID_TO_DELETE FROM PROJECTS WHERE PROJ_NAME_EN LIKE 'FD Project - CSB - A.1 - CFT - Final Reject of an Increase Movement - Seb';    
    IF PROJECT_ID_TO_DELETE IS NULL THEN
        DELETE FROM PROJECTS_ORG WHERE PROJ_ID = PROJECT_ID_TO_DELETE;
        DELETE FROM PROJECTS WHERE PROJ_ID  = PROJECT_ID_TO_DELETE;
        DELETE FROM MVT_ONGOING WHERE MVT_ONGOING_PROJ_ID  = PROJECT_ID_TO_DELETE;
        DELETE FROM MVT_HISTORY WHERE MVT_HISTORY_PROJ_ID  = PROJECT_ID_TO_DELETE;
    END IF;
    Insert into PROJECTS (PROJ_ID, ...) values (PROJECT_ID, ...);
    Insert into PROJECTS_ORG (PROJ_ID, ...) values (PROJECT_ID, ...);
    Insert into MVT_ONGOING (MVT_ONGOING_PROJ_ID, ...);
    Insert into MVT_HISTORY (PROJ_ID, ...) values (PROJECT_ID, ...);
END;

我收到“未找到数据”错误

您能帮我找到最佳优化解决方案吗？

谢谢

Answer 1

类似这样的：

DECLARE
   project_id_new        PLS_INTEGER;
   project_id_to_delete  PLS_INTEGER;
BEGIN
   BEGIN
      SELECT proj_id
        INTO project_id_to_delete
        FROM projects
       WHERE proj_name_en LIKE 'blabla';

      DELETE FROM projects_org WHERE proj_id = project_id_to_delete;
      DELETE FROM projects     WHERE proj_id = project_id_to_delete;
      DELETE FROM mvt_ongoing  WHERE mvt_ongoing_proj_id = project_id_to_delete;
      DELETE FROM mvt_history  WHERE mvt_history_proj_id = project_id_to_delete;
   EXCEPTION
      WHEN NO_DATA_FOUND
      THEN
         NULL;
   END;

   project_id_new := seq.nextval;
   
   INSERT INTO projects (project_id)     VALUES (project_id_new);
   INSERT INTO projects_org (project_id) VALUES (project_id_new);
END;

它有什么作用？

• 试图找到PROJ_ID
• 如果找到，执行DELETEs
  • 你不必使用IF；如果它被发现，它是已知的。如果未找到，则引发异常
• 否则，NO_DATA_FOUND 将引发异常并处理
  • 我选择了什么都不做，你可能想做点别的事情

在插入时（正如您评论的那样，您总是希望这样做）：将删除部分包含在其自己的 BEGIN-EXCEPTION-END 块中，以便处理可能的 no_data_found 错误。然后，找到project_id_new 值（例如，使用序列）并在INSERT 语句中使用它。