For Each Loop PL/SQL

Question

I am slowly learning PL/SQL, I have some programming experience using Visual Basic for Excel, so I am not totally in the dark, but not really sure :-)
Here is what I am trying to do, am on 10g by the way.
I have about 10+ Tables in my schema, with pretty much the same structure and I know that I could use plain SQL to do this with, but I want to learn PL/SQL.
So, I have 10+ tables where I have to add a new field of type varchar2(100), I was wondering if I could employ the FOR LOOP or maybe something better, list all the Tables that I need to ALTER and say:
For each Table from list
LOOP
alter table table_name add KEY varchar2(100);
END LOOP;
I have the full list of the Tables, what do you guys think ?

Answer 1

If you want to practice PL/SQL then this is the wrong task.
You would need to use dynamic SQL (execute immediate or dbms_sql) for this, but usually you should avoid dynamic SQL for many reasons.
As you already mentioned this can be easily done with SQL.
What I do in such cases is to build a select that returns me the 10+ alter table statements.
The oracle data dictionary (e.g. the view user_tables) has enough information to build such a select based on your requirements.
Then save the result into a file and run the file as a script in sql*plus.
example untested
select 'alter table '||t.table_name||' add KEY varchar2(100);'
from user_tables t
where t.table_name like 'XYZ%'
and t.table_name not in (select c.table_name from user_tab_columns c where column_name = 'KEY');Changes to the data structure in your database should not be done programatically (e.g by pl/sql) but should be entered into your version control system so that you can run the same script against your development database, against your test database and later against your production database.