oracle - 从表中选择DISTINCT CLOB_COLUMN；

Question

我想找到不同的CLOB值，这些值可以假定包含在名为COPIA的表中的CLOB_COLUMN列（CLOB类型）。

我选择了一种解决此问题的方法，但我希望给出一个简单的SELECT如下：SELECT DISTINCT CLOB_COLUMN FROM TABLE避免错误“ ORA-00932：不一致的数据类型：预期的-得到了CLOB”

我该如何实现？

预先感谢您的合作。这是我想过的程序方式：

-- Find the distinct CLOB values that can assume the column called CLOB_COLUMN (of type CLOB)
-- contained in the table called COPIA
-- Before the execution of the following PL/SQL script, the CLOB values (including duplicates) 
-- are contained in the source table, called S1
-- At the end of the excecution of the PL/SQL script, the distinct values of the column called CLOB_COLUMN
-- can be find in the target table called S2

BEGIN
   EXECUTE IMMEDIATE 'TRUNCATE TABLE S1 DROP STORAGE';

   EXECUTE IMMEDIATE 'DROP TABLE S1 CASCADE CONSTRAINTS PURGE';
EXCEPTION
   WHEN OTHERS
   THEN
      BEGIN
         NULL;
      END;
END;

BEGIN
   EXECUTE IMMEDIATE 'TRUNCATE TABLE S2 DROP STORAGE';

   EXECUTE IMMEDIATE 'DROP TABLE S2 CASCADE CONSTRAINTS PURGE';
EXCEPTION
   WHEN OTHERS
   THEN
      BEGIN
         NULL;
      END;
END;

CREATE GLOBAL TEMPORARY TABLE S1
ON COMMIT PRESERVE ROWS
AS
   SELECT CLOB_COLUMN FROM COPIA;

CREATE GLOBAL TEMPORARY TABLE S2
ON COMMIT PRESERVE ROWS
AS
   SELECT *
     FROM S1
    WHERE 3 = 9;

BEGIN
   DECLARE
      CONTEGGIO   NUMBER;

      CURSOR C1
      IS
         SELECT CLOB_COLUMN FROM S1;

      C1_REC      C1%ROWTYPE;
   BEGIN
      FOR C1_REC IN C1
      LOOP
         -- How many records, in S2 table, are equal to c1_rec.clob_column?
         SELECT COUNT (*)
           INTO CONTEGGIO
           FROM S2 BETA
          WHERE DBMS_LOB.
                 COMPARE (BETA.CLOB_COLUMN,
                          C1_REC.CLOB_COLUMN) = 0;

         -- If it does not exist, in S2, a record equal to c1_rec.clob_column, 
         -- insert c1_rec.clob_column in the table called S2
         IF CONTEGGIO = 0
         THEN
            BEGIN
               INSERT INTO S2
                    VALUES (C1_REC.CLOB_COLUMN);

               COMMIT;
            END;
         END IF;
      END LOOP;
   END;
END;

Answer 1

使用这种方法。在表概要文件中，列的内容为NCLOB。我添加了where子句以缩短运行时间，

with
  r as (select rownum i, content from profile where package = 'intl'),
  s as (select distinct (select min(i) from r where dbms_lob.compare(r.content, t.content) = 0) min_i from profile t where t.package = 'intl')
select (select content from r where r.i = s.min_i) content from s
;

它不会因为效率而赢得任何奖励，但是应该可以工作。