Working with very large text data and CLOB column

问题:

According to documentation CLOB and NCLOB datatype columns, can store up to 8 terabytes of character data.

I have text, which contains 100 000 character, how can I run query like this:

UPDATE my_table SET clob_column = 'text, which contains 100 000 characters' 
WHERE id = 1

?

If in text, character count is up to 32767, there is possible to use PL/SQL anonymous block:

DECLARE
   myvar VARCHAR2(15000);
BEGIN
    myvar := 'text, which contains 100 000 characters';
    UPDATE my_table SET clob_column = myvar
    WHERE id = 1;
    ....
 END; 

What is solution, where text is very large and contains for example 100 000 characters ?

update

I am trying with dbms_lob.append:

    create table t1 (c clob);

    declare
      c1 clob;
      c2 clob;
    begin
      c1 := 'abc';
      c2 := 'text, which contains 100 000 characters';
      dbms_lob.append(c1, c2);
      insert into t1 values (c1);
    end;

Though, also got error: string literal too long.

I am doing something wrong ?

回答1:

You should use the dbms_lob package, the procedure to add some string to the clob is dbms_lob.append.

DBMS_LOB documentation

declare
  c1 clob;
  c2 varchar2(32000);
begin
  c1 := 'abc';
  c2 := 'text, which contains 32 000 characters';
  dbms_lob.append(c1, c2);
  c2 := 'some more text, which contains 32 000 characters';
  dbms_lob.append(c1, c2);
  insert into t1 values (c1);
end;

回答2:

I found this question while Googling how to append data to a CLOB. For my particular problem, I'm using a legacy PL/SQL system where I can't make use of the dbms_lob package, so I thought that I would share my answer for the benefit of others in my situation.

Solution: Use Oracle's CONCAT function in aSELECTquery, theCONCATfunction works for theCLOB` data type. For example (using @AlenOblak's example):

declare
  c1 clob;
  c2 varchar2(32000);
begin
  c1 := 'abc';
  c2 := 'text, which contains 32 000 characters';
  SELECT CONCAT(c1, c2) INTO c1 FROM DUAL;
  c2 := 'some more text, which contains 32 000 characters';
  SELECT CONCAT(c1, c2) INTO c1 FROM DUAL;
  insert into t1 values (c1);
end;

Hope that helps.