PL/SQL referencing another cursor in a cursor?

问题

I'd like to create a procedure that selects all records that have been assigned to any particular user, then send one personalized email to each assigned user that contains a list of the records that are assigned to them.

So if myTable looks like this:

ID    Assigned
1     Joe
2     Joe
3     Shelly

Joe's email would display a line-delimited list with records 1 and 2 in it, and Shelly's would display record 3.

I started building a procedure with cursors at first, but 1) wasn't sure if I could reference a cursor within another cursor, and 2) don't know if a cursor is even the best approach for this.

My thought was that cursor 1 would get all unique Assigned values (Joe, Shelly) and cursor 2 would be executed inside the cursor 1 loop and get all records assigned to the current cursor 1 value.

Any insight or nudges in the appropriate direction would be greatly appreciated.

回答1:

It is possible to reference another cursor within the first one:

declare
  cursor c1 is
    select distinct Assigned from table_name;

  cursor c2(p_Assigned in varchar2) is
    select id, Assigned from table_name where Assigned = p_Assigned;
begin

  for r1 in c1 loop
    dbms_output.put_line('------- start mail --------');
    for r2 in c2(r1.Assigned) loop
      dbms_output.put_line(r2.id || ' ' || r2.Assigned);
    end loop;
    dbms_output.put_line('------- end mail -------');
  end loop;
end;

But you can do better, deppends on your version.
You can aggregate the records so in one query you'll get one record for each user with a column that contains the records concatenated with a newline:
here are some methods to this.
And you can also use xmlagg:

SELECT Assigned, rtrim(XMLAGG(xmlelement(e, id || ' ' || Assigned || chr(13)|| chr(10) )).extract('//text()'))
FROM table_name
GROUP BY Assigned

来源：https://stackoverflow.com/questions/9982883/pl-sql-referencing-another-cursor-in-a-cursor

标签

plsql

cursor