如何在 Oracle 中将 CLOB 转换为 CHAR 数据类型？
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How to convert CLOB to CHAR datatype in Oracle?
提问by Vignesh Kiswanth
For ETL Purpose, I need to convert DB records into flat-files. For that, I have to convert all the records as CHAR. In that table, it's having few columns with CLOB datatype. So, I tried the following functions:
出于 ETL 目的，我需要将数据库记录转换为平面文件。为此，我必须将所有记录转换为 CHAR。在那个表中，它有几个 CLOB 数据类型的列。所以，我尝试了以下功能：
DBMS.LOBS_SUBSTR(column_name, Length(column_name))
Error: ORA-06502 Pl/sql: numeric value error: character string buffer too small ORA-06512: at line 1 06502. 00000 - "PL/SQL: numeric or value error ℅s"
错误：ORA-06502 Pl/sql：数值错误：字符串缓冲区太小 ORA-06512：在第 1 行 06502. 00000 -“PL/SQL：数值或值错误 ℅s”
回答by Gurwinder Singh
You can use DBMS_LOB.substr()
您可以使用 DBMS_LOB.substr()
select DBMS_LOB.substr(col, 4000) from table;
Also, from the docs, restrictions are as:
此外，从docs，限制如下：
For fixed-width n-byte CLOBs, if the input amount for SUBSTR is greater than (32767/n), then SUBSTR returns a character buffer of length (32767/n), or the length of the CLOB, whichever is lesser. For CLOBs in a varying-width character set, n is the maximum byte-width used for characters in the CLOB
对于固定宽度的 n 字节 CLOB，如果 SUBSTR 的输入量大于 (32767/n)，则 SUBSTR 返回长度为 (32767/n) 的字符缓冲区，或 CLOB 的长度，以较小者为准。对于可变宽度字符集中的 CLOB，n 是用于 CLOB 中字符的最大字节宽度
