Pl/SQL- Get column names from a query

Question

I\'m using Pl/SQL with Oracle Database 11g.

I\'m writing a function that takes in a select statement as a parameter (varchar2). The function uses a for loop to go over

Answer 1

I believe you can use DESCRIBE_COLUMNS to do this. Just pass in the cursor and the other required parameters.

http://docs.oracle.com/cd/B19306_01/appdev.102/b14258/d_sql.htm#i1026120

declare
    v_sql varchar2(32767) := 'select 1 column1, 2 column2 from dual';
    v_cursor_id integer;
    v_col_cnt integer;
    v_columns dbms_sql.desc_tab;
begin
    v_cursor_id := dbms_sql.open_cursor;
    dbms_sql.parse(v_cursor_id, v_sql, dbms_sql.native);
    dbms_sql.describe_columns(v_cursor_id, v_col_cnt, v_columns);

    for i in 1 .. v_columns.count loop
        dbms_output.put_line(v_columns(i).col_name);
    end loop;

    dbms_sql.close_cursor(v_cursor_id);
exception when others then
    dbms_sql.close_cursor(v_cursor_id);
    raise;
end;
/

Output:
COLUMN1
COLUMN2

Answer 2

Based on dseibert's answer, I created function for usage:

create type cols_name
    as table of varchar2(32767)
/

CREATE OR REPLACE FUNCTION GET_COLUMNS_NAME(p_selectQuery IN VARCHAR2) RETURN cols_name PIPELINED IS
    v_cursor_id integer;
    v_col_cnt integer;
    v_columns dbms_sql.desc_tab;
begin
    v_cursor_id := dbms_sql.open_cursor;
    dbms_sql.parse(v_cursor_id, p_selectQuery, dbms_sql.native);
    dbms_sql.describe_columns(v_cursor_id, v_col_cnt, v_columns);

    for i in 1 .. v_columns.count loop
        pipe row(v_columns(i).col_name);
    end loop;

    dbms_sql.close_cursor(v_cursor_id);
    return;
exception when others then
    dbms_sql.close_cursor(v_cursor_id);
    raise;
end;
/

Using it:

select * from TABLE(get_columns_name('select 1 column1, 2 column2 from dual'));

Results:

**COLUMN_VALUE**
COLUMN1
COLUMN2