oracle中clob字段存入了一段字符串，现在我怎样一行行读取出来

Posted 2023-03-04

参考技术A 你插入的字符段落有分行符号吗？没有的话只能通过类似于跑马灯的形式展示出来本回答被提问者采纳 参考技术B to_char一下是否能够查看？

oracle如何操作clob数据类型

在存储过程里面，需要有个变量存储一段字符串，因为这段字符串可能很长，可能达到几万个字符，所以考虑用clob来存储，但是我在存储过程中如下写，报错message:=empty_clob();
DBMS_LOB.WRITEAPPEND(message, 10, '0123456789');说指定的lob定位符无效，谁知道如何往clob里面直接写入字符串，在线等。

在做数据库开发的时候，有时候会遇到需要读取Oracle数据库中的clob类型的数据的情况。本着代码复用的目的，写了下面的存储过程：读取数据库中clob字段的数据。

CREATE OR REPLACE PROCEDURE prc_read_clob(
table_name IN VARCHAR2,
clob_column_name IN VARCHAR2,
primary_Key_Column_names IN VARCHAR2,
primary_key_values IN VARCHAR2,
offset_i IN NUMBER,
read_length_i IN NUMBER,
RES OUT VARCHAR2,
total_length OUT NUMBER
) AS
/**
Autor:Hanks_gao.
Create Date:2008/12/10
Description:This procedure is to read clob value by conditions
--------------------------------------------------------------
-----------------Parameters descritption----------------------
table_name : The table that contains clob/blob columns(表名)
clob_column_name : Clob/blob column name of table_name(类型为clob的字段名)
primary_key_column_names : The columns seperated by '' that can fix only one row data (that is primary key) (主键名，以''分隔的字符串)
primary_key_values : The primary keyes values that seperated by ''(主键键值,以''分隔的字符串)
offset_i : The offset of reading clob data(要读取的位移量)
read_length_i : The length of reading clob data per times(要读取的长度)
res : Return value that can be referenced by application(读取的结果)
total_length : The total length of readed clob data(数据库查询到的clob数据的总长度)
-----------------End Parameters descritption------------------
*/

tmpPrimaryKeys VARCHAR2(2000); --To save primary_Key_Column_names temporarily(暂存主键,主键是以''分隔的字符串)
tmpPrimaryKeyValues VARCHAR2(2000); --To save primary_key_values temporarily(暂存主键键值,以''分隔的字符串)
i NUMBER; --循环控制变量
tmpReadLength NUMBER; --暂存要读取的长度
sqlStr VARCHAR2(6000); --Query string(查询字符串)
sqlCon VARCHAR2(5000); --Query condition(查询条件)

TYPE tmparray IS TABLE OF VARCHAR2(5000) INDEX BY BINARY_INTEGER;
arrayPrimaryKeys tmparray; --To save the analyse result of primary_Key_Column_names (暂存分析后得到的主键名)
arrayPrimaryKeyValues tmparray; --To save the analyse result of primary_key_values(暂存分析后得到的主键键值)
BEGIN
total_length := 0;
RES := '';
DECLARE
clobvar CLOB := EMPTY_CLOB;
BEGIN
tmpPrimaryKeys:=primary_Key_Column_names;
tmpPrimaryKeyValues:=primary_key_values;

i:=0;
WHILE INSTR(tmpPrimaryKeys,'')>0 LOOP --Analyse the column names of primary key(将主键分开,相当于arrayPrimaryKeys =tmpPrimaryKeys.split("") )
arrayPrimaryKeys(i):=subSTR(tmpPrimaryKeys,1,(INSTR(tmpPrimaryKeys,'')-1));
tmpPrimaryKeys:=subSTR(tmpPrimaryKeys,(INSTR(tmpPrimaryKeys,'')+1));
i:=i+1;
END LOOP;

i:=0;
WHILE INSTR(tmpPrimaryKeyValues,'')>0 LOOP --Analyse the values of primary key
arrayPrimaryKeyValues(i):=subSTR(tmpPrimaryKeyValues,1,(INSTR(tmpPrimaryKeyValues,'')-1));
tmpPrimaryKeyValues:=subSTR(tmpPrimaryKeyValues,(INSTR(tmpPrimaryKeyValues,'')+1));
i:=i+1;
END LOOP;

IF arrayPrimaryKeys.COUNT()<>arrayPrimaryKeyValues.COUNT() THEN --判断键与键值是否能匹配起来
res:='KEY-VALUE NOT MATCH';
RETURN;
END IF;

i := 0;
sqlCon := '';
WHILE i < arrayPrimaryKeys.COUNT() LOOP
sqlCon := sqlCon || ' AND ' || arrayPrimaryKeys(i) || '='''
|| replace(arrayPrimaryKeyValues(i),'''','''''') || '''';
i := i + 1;
END LOOP;

sqlStr := 'SELECT ' || clob_column_name || ' FROM ' || table_name
|| ' WHERE 1=1 ' || sqlCon || ' AND ROWNUM = 1' ; --组查询字符串

dbms_lob.createtemporary(clobvar, TRUE);
dbms_lob.OPEN(clobvar, dbms_lob.lob_readwrite);

EXECUTE IMMEDIATE TRIM(sqlStr) INTO clobvar; --执行查询

IF offset_i <= 1 THEN
total_length:=dbms_lob.getlength(clobvar);
END IF;

IF read_length_i <=0 THEN
tmpReadLength := 4000;
ELSE
tmpReadLength := read_length_i;
END IF;

dbms_lob.READ(clobvar,tmpReadLength,offset_i,res); --读取数据

IF dbms_lob.ISOPEN(clobvar)=1 THEN
dbms_lob.CLOSE(clobvar);
END IF;

END;
EXCEPTION
WHEN OTHERS THEN
res:='';
total_length:=0;
END; 参考技术A clob 类型的操作很容易的，可以当成 varchar2 一样处理。blob处理上才困难一些。