On the third week, the developer came to me for some help. He said his code was slow. So he decided to dynamically drop all the triggers on the table he was working with. He wanted to issue an ALTER TABLE command from his script, which consisted of one large PL/SQL block. Of course it was not working. I told him you can't just drop a DDL statement in the middle of that block. You can only do that for DML. However you can run the DDL inside an EXECUTE IMMEDIATE. He seemed happy.
Later the same guy came back and said he was still having problems. The error indicated that the table he was trying to access did not exist. Well I told him that the table is most likely there. But he was running the script as a different user. I thought there was a public synonym which should have let his script resolve the table name. The guy was in a hurry. So I told him he could qualify the table name with the schema name prepended. That got him a bit further.
The problems this guy was running into stemmed from some lack of knowledge. And experience is the best teacher here. He had a lot more pain. For some reason he chose the wrong type for one parameter he was passing. Then when he used the variable of wrong type, Oracle needed to convert the value, causing it to not use the index that was needed to make everything fast. Ah this should not be this hard.
