如何在pl / sql中的另一個游標的select語句中使用游標中的變量

Question

我想運行查詢，獲取結果，然后使用第二個語句（游標）中第一個語句的值，使用另一個select語句迭代該查詢的結果。

我的數據庫中有40個用戶。 所有用戶都具有相同的數據庫架構結構。 我想通過以下方式獲取用戶名：

SELECT  distinct username 
   from all_users 

然后使用用戶名運行如下查詢：

Select lastname, firstname, email, email2 from username.member.

我的結果集將返回多行，所以我也需要一個行類型。

我嘗試了很多不同的pl / sql組合：

DECLARE
   CURSOR client_cur IS
   SELECT  distinct username 
   from all_users 
   where length(username) = 3;
   -- client cursor 
   CURSOR emails_cur (cli all_users.username%TYPE) IS
   SELECT id, name 
     FROM cli.org;
BEGIN
   FOR client IN client_cur LOOP
      dbms_output.put_line('Client is '|| client.username);
      FOR email_rec in client_cur(client.username) LOOP
         dbms_output.put_line('Org id is ' ||email_rec.id || ' org nam ' || email_rec.name);
      END LOOP;
  END LOOP;
END;
/

和

DECLARE
  CURSOR c1 IS
    SELECT  distinct username from all_users where length(username) = 3;
    client c1%rowtype;
   cursor c2 is Select id, name, allow_digest_flg from c1.username.org;
 digest c2%rowtype;
-- declare record variable that represents a row fetched from the employees table
--   employee_rec c1%ROWTYPE; 
 BEGIN
-- open the explicit cursor and use it to fetch data into employee_rec
    OPEN c1;
  loop
     FETCH c1 INTO client; 
   open c2; 
   loop
    fetch c2 into digest;
      DBMS_OUTPUT.PUT_LINE('digest is : ' || c2.id || ' and name is ' || c2.name || ' flg is ' || c2.allow_digest_flg );
   end loop;
  end loop;
 END;
/

這些和其中的許多變化。

有人能幫我嗎。 謝謝

Answer 1

您需要使用動態SQL來實現此目的; 就像是：

DECLARE
    TYPE cur_type IS REF CURSOR;

    CURSOR client_cur IS
        SELECT DISTING username
        FROM all_users
        WHERE length(username) = 3;

    emails_cur cur_type;
    l_cur_string VARCHAR2(128);
    l_email_id <type>;
    l_name <type>;
BEGIN
    FOR client IN client_cur LOOP
        dbms_output.put_line('Client is '|| client.username);
        l_cur_string := 'SELECT id, name FROM '
            || client.username || '.org';
        OPEN emails_cur FOR l_cur_string;
        LOOP
            FETCH emails_cur INTO l_email_id, l_name;
            EXIT WHEN emails_cur%NOTFOUND;
            dbms_output.put_line('Org id is ' || l_email_id
                || ' org name ' || l_name);
        END LOOP;
        CLOSE emails_cur;
    END LOOP;
END;
/

編輯糾正兩個錯誤，並為OPEN-FOR添加10g文檔的鏈接和示例 。 編輯使內部游標查詢字符串變量。

Answer 2

你當然可以做類似的事情

SQL> ed
Wrote file afiedt.buf

  1  begin
  2    for d in (select * from dept)
  3    loop
  4      for e in (select * from emp where deptno=d.deptno)
  5      loop
  6        dbms_output.put_line( 'Employee ' || e.ename ||
  7                              ' in department ' || d.dname );
  8      end loop;
  9    end loop;
 10* end;
SQL> /
Employee CLARK in department ACCOUNTING
Employee KING in department ACCOUNTING
Employee MILLER in department ACCOUNTING
Employee smith in department RESEARCH
Employee JONES in department RESEARCH
Employee SCOTT in department RESEARCH
Employee ADAMS in department RESEARCH
Employee FORD in department RESEARCH
Employee ALLEN in department SALES
Employee WARD in department SALES
Employee MARTIN in department SALES
Employee BLAKE in department SALES
Employee TURNER in department SALES
Employee JAMES in department SALES

PL/SQL procedure successfully completed.

或使用顯式游標等效的東西。

SQL> ed
Wrote file afiedt.buf

  1  declare
  2    cursor dept_cur
  3        is select *
  4             from dept;
  5    d dept_cur%rowtype;
  6    cursor emp_cur( p_deptno IN dept.deptno%type )
  7        is select *
  8             from emp
  9            where deptno = p_deptno;
 10    e emp_cur%rowtype;
 11  begin
 12    open dept_cur;
 13    loop
 14      fetch dept_cur into d;
 15      exit when dept_cur%notfound;
 16      open emp_cur( d.deptno );
 17      loop
 18        fetch emp_cur into e;
 19        exit when emp_cur%notfound;
 20        dbms_output.put_line( 'Employee ' || e.ename ||
 21                              ' in department ' || d.dname );
 22      end loop;
 23      close emp_cur;
 24    end loop;
 25    close dept_cur;
 26* end;
 27  /
Employee CLARK in department ACCOUNTING
Employee KING in department ACCOUNTING
Employee MILLER in department ACCOUNTING
Employee smith in department RESEARCH
Employee JONES in department RESEARCH
Employee SCOTT in department RESEARCH
Employee ADAMS in department RESEARCH
Employee FORD in department RESEARCH
Employee ALLEN in department SALES
Employee WARD in department SALES
Employee MARTIN in department SALES
Employee BLAKE in department SALES
Employee TURNER in department SALES
Employee JAMES in department SALES

PL/SQL procedure successfully completed.

但是，如果您發現自己使用嵌套游標FOR循環，那么讓數據庫為您加入兩個結果幾乎總是更有效。 畢竟，關系數據庫真的非常善於加入。 我在這里猜測你的桌子是什么樣的，以及它們是如何根據你發布的代碼相關聯的

FOR x IN (SELECT *
            FROM all_users,
                 org
           WHERE length(all_users.username) = 3
             AND all_users.username = org.username )
LOOP
  <<do something>>
END LOOP;

Answer 3

使用alter session set current_schema = <username> ，在您的情況下作為執行立即數。

有關詳細信息，請參閱Oracle的文檔 。

在你的情況下，這可能歸結為（ 未經測試 ）

DECLARE

   CURSOR client_cur IS
     SELECT  distinct username 
       from all_users 
      where length(username) = 3;

   -- client cursor 
   CURSOR emails_cur IS
   SELECT id, name 
     FROM org;

BEGIN

   FOR client IN client_cur LOOP

   -- ****
      execute immediate 
     'alter session set current_schema = ' || client.username;
   -- ****

      FOR email_rec in client_cur LOOP

         dbms_output.put_line(
             'Org id is ' || email_rec.id || 
             ' org nam '  || email_rec.name);

      END LOOP;

  END LOOP;
END;
/