为什么立即执行会引发此PLS-00201错误？

Question

I was trying to run the following code and it failed in the execute immediate block. So, am I going wrong with the syntax?

DECLARE
  l_data long; 
  emp_rec EMP%rowtype;
begin 

  select *  INTO emp_rec  from EMP A WHERE A.EMP_NO = '001322';

 for x in ( select column_name, data_type 
            from user_tab_columns 
             where table_name = 'EMP' ) 
 loop 
   execute immediate 
      'begin 
        :x := emp_rec.' || x.column_name || '; 
      end;' using OUT l_data; 

     dbms_output.put_line( x.column_name || ' = ' || l_data ); 

  end loop; 

end; 

I get this error

PLS-00201: Identifier EMP_REC.EMP_NO must be declared

Answer 1

Your emp_rec variable is a local PL/SQL record. When you do this, even with a static field name reference:

 execute immediate 'begin :x := emp_rec.emp_no; end;' 

the dynamic SQL runs in a separate context to the block that calls it. You then run a new anonymous PL/SQL block within that context.

Any variables from your outer anonymous block, specifically emp_rec here, are out of scope to the dynamic SQL context. They just do not exist to the code that is trying to assign the value to :x .

You could possibly do something with dbms_sql to make this dynamic, but if you know the table columns it would be easier to do:

declare
  l_data varchar2(4000); -- long is deprecated; how big does this really need to be?
  emp_rec EMP%rowtype;
begin 
  select *  INTO emp_rec  from EMP A WHERE A.EMP_NO = '001322';

  for x in (
    select column_name, data_type 
    from user_tab_columns 
    where table_name = 'EMP'
  ) 
  loop
    case x.column_name
      when 'EMP_NO' then
        l_data := emp_rec.emp_no;
      -- when clauses for each column in your real table
      when 'FIRST_NAME' then
        l_data := emp_rec.first_name;
      when 'LAST_NAME' then
        l_data := emp_rec.last_name;
      -- list other columns and assignments
      -- else ...
    end case;

    dbms_output.put_line( x.column_name || ' = ' || l_data ); 
  end loop; 
end; 
/

although as @APC pointed out, the loop is now a bit pointless, since you can just do:

declare
  emp_rec EMP%rowtype;
begin 
  select *  INTO emp_rec  from EMP A WHERE A.EMP_NO = '001322';

  dbms_output.put_line( 'EMP_NO = ' || emp_rec.emp_no ); 
  dbms_output.put_line( 'FIRST_NAME = ' || emp_rec.first_anme ); 
  dbms_output.put_line( 'LAST_NAME = ' || emp_rec.last_name ); 
  -- ... any other columns you want to show
end; 
/

Answer 2

The emp_rec in the EXECUTE IMMEDIATE statement exists in a different namespace from the emp_rec in the calling code.

Not sure exactly what you're trying to achieve but it might be something like this:

DECLARE
     l_data long; 
     emp_rec EMP%rowtype;
begin 
      select *  INTO emp_rec  from EMP A WHERE A.EMP_NO = '001322';
     for x in ( select column_name, data_type 
            from user_tab_columns 
            where table_name = 'EMP' ) 
     loop 
         execute immediate 
         'declare
           lrec EMP%rowtype;
         begin 
            lrec := :emp_rec;
             :x := lrec.' || x.column_name || '; 
         end;' using  emp_rec, OUT l_data; 

         dbms_output.put_line( x.column_name || ' = ' || l_data ); 

     end loop; 
end; 

---

Note: I tested a version of this code in 12C and it does work there. Alas it doesn't work in 11gR2 (and presumably earlier versions too); it hurls PLS-00457 . Still, 11gR2 is pretty much out of support except for folks with deep pockets, everybody ought to be using 12c by now:)

Answer 3

My guess would be that you have a hidden column in your emp table. Those are columns that've been marked as unused but not yet dropped, and as such, they are not available to be selected from.

You could update your cursor to use:

 select column_name, data_type 
 from   user_tab_cols 
 where  table_name = 'EMP'
 and    hidden_column != 'NO'

or:

 select column_name, data_type 
 from   user_tab_columns 
 where  table_name = 'EMP';

Note the different view name used in both queries - user_tab_columns doesn't output rows for hidden columns, whereas user_tab_cols does so you have to explicitly filter them out if you don't want to see them.