sql - insert if not exists

Question

I am having trouble with a sql query. I need to insert a row if the same row does not exist already. This is what I have so far:

DECLARE
BEGIN
   FOR FOLDE         


        

Answer 1

Do it all in SQL rather than context switching into 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);

Answer 2

A better (Oracle specific?) solution may be the MERGE statement.

See here for a nice explanation, with examples:

http://www.oracle-base.com/articles/10g/MergeEnhancements10g.php

Hope that helps.

Answer 3

You forgot the THEN

IF condition THEN  
   ...
ELSE
    ...
END IF;

Answer 4

DECLARE
    N_COUNTS NUMBER;
BEGIN
    select count(ID) into N_COUNTS from TABLE_NAME where ID = 1;
    IF N_COUNTS=0 THEN
        INSERT QUERY....
    ELSE
        UPDATE QUERY....
    END IF;
END;