This question has NOTHING to do with sql developer so please mark it ANSWERED and repost it at:
Also you can NOT execute sql statements in pl/sql without using a clause to tell Oracle where to put the data
- value => 'begin
- select sysdate from dual;
Where do you expect Oracle to put the value of SYSDATE that the query returns?
You need to test your code MANUALLY before you try to automate it. If you need further help repost your question in the proper forum.