PL/SQL 使用通用输入写入文件

Question

我最近创建了一个 PL/SQL 程序，它根据数据库中的相关数据创建五个不同的竖线分隔文件。

我找不到一种方法将不同的表格数据（在这种情况下为游标）动态提取到创建文件的通用过程中。相反，我不得不创建五个单独的过程，一个用于每个文件，它接收五个不同的光标，一个用于每个文件需求记录选择。

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要找的东西。

如何在 PL/SQL 中实现此目的？

我想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。

Answer 1

将光标作为 SYS_REFCURSOR 传递到您的过程中。然后，使用 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，并使用DBMS_SQL.DEFINE_COLUMN、DBMS_SQL.FETCH_ROWS和DBMS_SQL.VALUE从游标中获取数据到PL/SQL 变量。然后，将 PL/SQL 变量写入输出文件。

这里有一些代码可以为您将所有这些组合在一起。

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;

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