获取CLOB列的子字符串并使用具有大小/缓冲区限制的查询工具时，有时需要将BUFFER设置为更大的大小.例如，在使用SQL Plus时，使用SET BUFFER 10000将其设置为10000，默认值为4000.

When getting the substring of a CLOB column and using a query tool that has size/buffer restrictions sometimes you would need to set the BUFFER to a larger size. For example while using SQL Plus use the SET BUFFER 10000 to set it to 10000 as the default is 4000.

运行DBMS_LOB.substr命令，您还可以指定要返回的字符数和偏移量.因此，使用DBMS_LOB.substr(column, 3000)可能会将其限制为缓冲区的足够小量.

Running the DBMS_LOB.substr command you can also specify the amount of characters you want to return and the offset from which. So using DBMS_LOB.substr(column, 3000) might restrict it to a small enough amount for the buffer.

请参见 Oracle文档有关substr命令的更多信息

See oracle documentation for more info on the substr command

    DBMS_LOB.SUBSTR (
       lob_loc     IN    CLOB   CHARACTER SET ANY_CS,
       amount      IN    INTEGER := 32767,
       offset      IN    INTEGER := 1)
      RETURN VARCHAR2 CHARACTER SET lob_loc%CHARSET;