sql - 如果不存在则插入

Question

我在使用SQL查询时遇到问题.如果已经存在相同的行,我需要插入一行.这是我到目前为止:

DECLARE
BEGIN
   FOR FOLDER_ROW IN (SELECT FOLDERID, USERID FROM DATA1.FOLDERS)
      LOOP                       
          IF NOT EXISTS (SELECT * FROM DATA1.FOLDER_USER WHERE FOLDER_ID = FOLDER_ROW.FOLDERID AND USER_ID = FOLDER_ROW.USERID) 
          INSERT INTO DATA1.FOLDER_USER (FOLDER_ID, USER_ID) VALUES (FOLDER_ROW.FOLDERID, FOLDER_ROW.USERID);
     END LOOP;
    COMMIT;
END;

我不会非常熟悉sql特别是不存在的语法所以当我执行时我得到以下错误:

ORA-06550:第37行,第11列:PLS-00103:当遇到以下情况之一时遇到符号"INSERT":

然后和或

符号"then"代替"INSERT"继续.

ORA-06550: line 38, column 10:
PLS-00103: Encountered the symbol "LOOP" when expecting one of the following:

   if
ORA-06550: line 40, column 5:
PLS-00103: Encountered the symbol "end-of-file" when expecting one of the following:

   end not pragma final instantiable order overriding static
   member constructor map

Answer 1

在SQL中完成所有操作而不是上下文切换到PL/SQL:

INSERT INTO DATA1.FOLDERS
(folder_id,
 user_id)
SELECT f1.folder_id,
       f1.user_id
  FROM DATA1.FOLDERS f1
 WHERE NOT EXISTS (SELECT 1
                     FROM DATA1.FOLDERS f2
                    WHERE f1.folder_id = f2.folder_id
                      AND f1.user_id = f2.user_id);