How to import and export CLOB fields in PL/SQL?

1 year ago
Liam
2 minutes

In PL/SQL, you can use the DBMS_LOB package to import and export CLOB fields.

To export a CLOB field, you can use the GETLENGTH function from the DBMS_LOB package to get the length of the CLOB field, and use the READ function from the DBMS_LOB package to read the content of the CLOB field. Here is an example:

DECLARE
  l_clob CLOB;
  l_length NUMBER;
  l_buffer VARCHAR2(32767);
  l_offset NUMBER := 1;
BEGIN
  -- 从表中获取CLOB字段
  SELECT clob_column INTO l_clob FROM your_table WHERE id = 1;
  
  -- 获取CLOB字段的长度
  l_length := DBMS_LOB.GETLENGTH(l_clob);
  
  -- 循环读取CLOB字段的内容
  WHILE l_offset <= l_length LOOP
    DBMS_LOB.READ(l_clob, 32767, l_offset, l_buffer);
    
    -- 在这里可以处理读取到的内容，比如写入文件或者输出到屏幕
    -- ...
    
    l_offset := l_offset + 32767;
  END LOOP;
END;

To import a CLOB field, you can use the CREATE_TEMPORARY function within the DBMS_LOB package to create a temporary CLOB object, and then use the WRITE function within the DBMS_LOB package to write the content into the CLOB field. Here is an example:

DECLARE
  l_clob CLOB;
  l_buffer VARCHAR2(32767);
BEGIN
  -- 创建临时的CLOB对象
  l_clob := DBMS_LOB.CREATE_TEMPORARY(CACHE => FALSE, TRUE);
  
  -- 循环写入内容到CLOB字段
  FOR i IN 1..10 LOOP
    -- 在这里可以读取文件或者输入的内容，并将其赋值给l_buffer变量
    -- ...
    
    DBMS_LOB.WRITEAPPEND(l_clob, LENGTH(l_buffer), l_buffer);
  END LOOP;
  
  -- 在这里可以将l_clob对象插入到表中的CLOB字段
  -- ...
  
  -- 释放临时的CLOB对象
  DBMS_LOB.FREETEMPORARY(l_clob);
END;

The above is one way to import and export CLOB fields, you can also make appropriate modifications according to your own needs.

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