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我最近创建了一个 PL/SQL 程序，它从数据库中的相关数据创建五个不同的管道分隔文件。

在这种情况下，我找不到将不同的表格数据动态拉入到创建文件的通用过程中的方法。相反，我必须创建五个单独的过程，每个文件一个，接收五个不同的游标，每个文件需求记录选择一个。

我不禁认为必须有更好的方法。我正在研究参考游标，但我不认为它们正是我正在寻找的。

如何在 PL/SQL 中实现这一点？

我认为我正在寻找的是一些通用类型，它可以在给定任意数量的记录和记录列的情况下从游标中获取任何数据，并且能够查询自身以查找其中的数据。

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1 回答 1

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将光标作为SYS_REFCURSOR. 然后，用于DBMS_SQL.TO_CURSOR_NUMBER();将 ref 游标转换为 DBMS_SQL 游标。

然后，使用DBMS_SQL.DESCRIBE_COLUMNS找出游标中的列 和DBMS_SQL.DEFINE_COLUMN，DBMS_SQL.FETCH_ROWS并将游标DBMS_SQL.VALUE中的数据获取到 PL/SQL 变量中。然后，将 PL/SQL 变量写入输出文件。

这里有一些代码可以为你把所有这些放在一起。

DECLARE
  l_rc SYS_REFCURSOR; 

PROCEDURE dump_cursor (p_rc IN OUT SYS_REFCURSOR) IS
  -- Dump the results of p_rc to log

  l_cursor                INTEGER;
  l_column_count          INTEGER;
  l_column_descriptions   SYS.DBMS_SQL.desc_tab;
  l_status                INTEGER;
  l_column_value          VARCHAR2 (4000);
  l_column_width          NUMBER;
  l_rec_count             NUMBER := 0;
  l_line                  VARCHAR2 (4000);


  FUNCTION get_length (l_column_def IN SYS.DBMS_SQL.desc_rec)
    RETURN NUMBER IS
    l_width   NUMBER;
  BEGIN
    l_width   := l_column_def.col_max_len;
    l_width   := CASE l_column_def.col_type WHEN 12 THEN                                                      /* DATE */
                                                        20 WHEN 2 THEN                                      /* NUMBER */
                                                                      10 ELSE l_width END;
    -- Don't display more than 256 characters of any one column (this was my requirement -- your file writer probably doesn't need to do this
    l_width   := LEAST (256, GREATEST (l_width, l_column_def.col_name_len));
    RETURN l_width;
  END get_length;
BEGIN
  -- This is the date format that I want to use for dates in my output
  EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY HH24:MI:SS''';

  l_cursor   := sys.DBMS_SQL.to_cursor_number (p_rc);

  -- Describe columns
  sys.DBMS_SQL.describe_columns (c => l_cursor, col_cnt => l_column_count, desc_t => l_column_descriptions);

  l_line     := '';

  FOR i IN 1 .. l_column_count LOOP
    l_column_width   := get_length (l_column_descriptions (i));

    l_line           := l_line || RPAD (l_column_descriptions (i).col_name, l_column_width);
    l_line           := l_line || ' ';
    DBMS_SQL.define_column (l_cursor,
                            i,
                            l_column_value,
                            4000);
  END LOOP;

  DBMS_OUTPUT.put_line (l_line);

  l_line     := '';

  FOR i IN 1 .. l_column_count LOOP
    l_column_width   := get_length (l_column_descriptions (i));

    l_line           := l_line || RPAD ('-', l_column_width, '-');
    l_line           := l_line || ' ';
    DBMS_SQL.define_column (l_cursor,
                            i,
                            l_column_value,
                            4000);
  END LOOP;

  DBMS_OUTPUT.put_line (l_line);

  --   l_status   := sys.DBMS_SQL.execute (l_cursor);

  WHILE (sys.DBMS_SQL.fetch_rows (l_cursor) > 0) LOOP
    l_rec_count   := l_rec_count + 1;

    l_line        := '';

    FOR i IN 1 .. l_column_count LOOP
      DBMS_SQL.COLUMN_VALUE (l_cursor, i, l_column_value);
      l_column_value   := TRANSLATE (l_column_value, CHR (10), CHR (200));
      l_column_width   := get_length (l_column_descriptions (i));

      IF l_column_value IS NULL THEN
        l_line   := l_line || RPAD (' ', l_column_width);
      ELSE
        l_line   := l_line || RPAD (l_column_value, l_column_width);
      END IF;

      l_line           := l_line || ' ';
    END LOOP;

    DBMS_OUTPUT.put_line (l_line);
  END LOOP;

  IF l_rec_count = 0 THEN
    DBMS_OUTPUT.put_line ('No data found.');
  ELSE
    DBMS_OUTPUT.put_line (l_rec_count || ' rows returned.');
  END IF;

  sys.DBMS_SQL.close_cursor (l_cursor);

  -- It would be better to store the current NLS_DATE_FORMAT on entry and restore it here, instead of assuming that it was
  -- set to DD-MON-YYYY.
  EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY''';
EXCEPTION
  WHEN OTHERS THEN
    EXECUTE IMMEDIATE 'alter session set nls_date_format=''DD-MON-YYYY''';
-- Add your own handling here.

END dump_cursor;

-- Tester code, make sure server output is on
BEGIN
  OPEN l_rc FOR 'SELECT object_id, object_name, object_type FROM dba_objects WHERE rownum <= 15';
  dump_cursor(l_rc);
END;
于 2015-10-28T20:13:38.490 回答