Question

I am attempting to write a generic trigger that can inspect each tuple that is to be inserted into the database. In this inspection I want to replace characters that are of interest to me, such as the curly quotation mark (MS word) with the regular quotation mark (“). Since I do not want to have to write two replace calls for each column that stores data that the user supplies, nor do I want to do this in the application for a myriad of reasons. pseudocode as follows:

create or replace trigger changeChars
before insert  
on @tableName  
reference new as var
for each row  
Begin 
loop  
:var.@column  := replace(:var.@column,'”', '"');   
end 

Answer 1

Why do you want to replace these characters? A lot of folks have problems with characters like the Microsoft curly quotes because those characters are not supported by their database character set which, by default, causes character set conversion to replace those characters with replacement characters like ‘?’. If that is the problem that you’re trying to solve, database code can’t help because the character set conversion happens at the network layer before the data even gets to the database. Potentially, you could use Oracle Locale Builder to build a custom locale for your client machines that would allow you to specify different replacement characters (i.e. double-quotes rather than Microsoft curly quotes).

If your problem is not character set related, there is no way to create this sort of dynamic trigger. You could write a bit of dynamic SQL that created a trigger for every table that called REPLACE on every VARCHAR2 column in the table. Of course, you’d need to maintain the trigger every time an additional VARCHAR2 column was added (either by changing the trigger or re-running the PL/SQL block).

Untested, and I’m sure the DDL generated isn’t correct, but you’d want something like

DECLARE
  l_sql_stmt VARCHAR2(4000);
BEGIN
  FOR tbl IN (SELECT * FROM user_tables)
  LOOP
    l_sql_stmt := 'CREATE OR REPLACE TRIGGER ' || tbl.table_name || '_changeChars ' ||
                  '  BEFORE INSERT ON ' || tbl.table_name ||
                  '  FOR EACH ROW ' ||
                  'BEGIN ';
    FOR col IN (SELECT * FROM user_tab_cols WHERE table_name = tbl.table_name)
    LOOP
      l_sql_stmt := l_sql_stmt ||
                    ' :new.' || col.column_name || 
                        ' := replace( :new.' || col.column_name || ',''"'', ''"''');';
    END LOOP;
    l_sql_stmt := l_sql_stmt || 
                    'END; ';
    dbms_output.put_line( 'SQL statement = ' || l_sql_stmt );
    EXECUTE IMMEDIATE l_sql_stmt;
  END LOOP;
END;