How to view the type of a variable in PL/SQL?

问题:

Is there a function in PL/SQL to show a variable's exact type, like the DUMP function in SQL?

I've tried the following

DECLARE
   l_variable   INTEGER := 1;
BEGIN
   DBMS_OUTPUT.PUT_LINE (DUMP (l_variable));
END;

But it gives the following error:

PLS-00204: function or pseudo-column 'DUMP' may be used inside a SQL statement only

回答1:

You can create this function using PL/Scope. But it won't work with anonymous blocks, and you'll need to reference the variable as a string.

create or replace function get_plsql_type_name
(
    p_object_name varchar2,
    p_name varchar2
) return varchar2 is
    v_type_name varchar2(4000);
begin
    select reference.name into v_type_name
    from user_identifiers declaration
    join user_identifiers reference
        on declaration.usage_id = reference.usage_context_id
        and declaration.object_name = reference.object_name
    where
        declaration.object_name = p_object_name
        and declaration.usage = 'DECLARATION'
        and reference.usage = 'REFERENCE'
        and declaration.name = p_name;

    return v_type_name;
end;
/

Example:

alter session set plscope_settings = 'IDENTIFIERS:ALL';

create or replace type my_weird_type is object
(
    a number
);

create or replace procedure test_procedure is
    var1 number;
    var2 integer;
    var3 my_weird_type;
    subtype my_subtype is pls_integer range 42 .. 43;
    var4 my_subtype;
begin
    dbms_output.put_line(get_plsql_type_name('TEST_PROCEDURE', 'VAR1'));
    dbms_output.put_line(get_plsql_type_name('TEST_PROCEDURE', 'VAR2'));
    dbms_output.put_line(get_plsql_type_name('TEST_PROCEDURE', 'VAR3'));
    dbms_output.put_line(get_plsql_type_name('TEST_PROCEDURE', 'VAR4'));
end;
/

begin
    test_procedure;
end;
/

NUMBER
INTEGER
MY_WEIRD_TYPE
MY_SUBTYPE

回答2:

as you should notice, DUMP is an overloaded function. it has 3 overloads.

So you can simulate the same thing within your code.

function myDump (x Varchar2) return varchar2 is begin return('string') ; end ;
function myDump (x number) return varchar2 is begin return('integer') ; end ;
function myDump (x date) return varchar2 is begin return('date') ; end ;

the above code may not work properly but should give you the idea how to deal the problem.

I hope that this will fulfil your requirements.

Note; you can put these functions in a Package and use them accordingly.

回答3:

declare
  a number(10,3);
  type_info varchar2(400);
begin
  a := 55.5;
  select dump(a) into type_info from dual;
  DBMS_OUTPUT.PUT_LINE(type_info);
end;