sql - CLOB 字段上的子字符串

Question

我们正在尝试在 CLOB 字段中应用子字符串函数来修剪前 4000 个字符。我们收到以下错误消息。

下面是我们正在使用的查询:

select
cast(substr(field_name,1,4000) as varchar(4000))
from table_name;

错误报告:

SQL Error: ORA-22835: Buffer too small for CLOB to CHAR or BLOB to RAW conversion (actual: 8000, maximum: 4000)
22835. 00000 - "Buffer too small for CLOB to CHAR or BLOB to RAW conversion (actual: %s, maximum: %s)"
*Cause: An attempt was made to convert CLOB to CHAR or BLOB to RAW, where the LOB size was bigger than the buffer limit for CHAR and RAW types. Note that widths are reported in characters if character length semantics are in effect for the column, otherwise widths are reported in bytes.
*Action: Do one of the following 1. Make the LOB smaller before performing the conversion, for example, by using SUBSTR on CLOB 2. Use DBMS_LOB.SUBSTR to convert CLOB to CHAR or BLOB to RAW.

Answer 1

替代使用 dbms_lob.substr :

dbms_lob.substr(clob_field_name, desired_size)

不需要转换。