如何将LONG数据转换为TIMESTAMP或VARCHAR2？

Question

我需要这样的东西:

SELECT PARTITION_NAME,
       to_char(LONG_TO_TIMESTAMP(HIGH_VALUE), 'MM/DD/YYYY HH24:MI:SS') AS HIGH_VAL
  FROM USER_TAB_PARTITIONS
 WHERE TABLE_NAME = 'TABLE_NAME'

输出应该如下所示:

PARTITION_NAME HIGH_VAL
---------------- --------------------
SOME_NAME 01/01/2010 00:00:00

当我跑:

SELECT PARTITION_NAME,来自USER_TAB_PARTITIONS的HIGH_VALUE

看起来像:

PARTITION_NAME HIGH_VAL
---------------- --------------------
SOME_NAME TIMESTAMP'2010-01-01 00:00:00'

如果我使用UTL_RAW.CAST_TO_VARCHAR2(HIGH_VALUE),
我最终会收到ORA-00997: illegal use of LONG datatype错误.

如果我使用''||HIGH_VALUEor to_clob(HIGH_VALUE)或to_char(HIGH_VALUE),
我会收到ORA-00932: inconsistent datatypes: expected [DATA_TYPE] got LONG错误

我的工作功能归功于shobi:

CREATE OR REPLACE FUNCTION GET_HIGH_VALUE_AS_DATE (
    p_TableName     IN VARCHAR2,
    p_PatitionName  IN VARCHAR2
) RETURN DATE
IS
   v_LongVal LONG;
BEGIN
    SELECT HIGH_VALUE INTO v_LongVal
      FROM USER_TAB_PARTITIONS
     WHERE TABLE_NAME = p_TableName
       AND PARTITION_NAME = p_PatitionName;

    RETURN TO_DATE(substr(v_LongVal, 11, 19), 'YYYY-MM-DD HH24:MI:SS');
END GET_HIGH_VALUE_AS_DATE;

SQL看起来像

SELECT PARTITION_NAME, GET_HIGH_VALUE_AS_DATE(TABLE_NAME, PARTITION_NAME)
  FROM USER_TAB_PARTITIONS
 WHERE TABLE_NAME LIKE 'TABLE_NAME'
   AND ROWNUM < 2;

Answer 1

转换LONG列的唯一方法是PL/SQL.请查看以下示例,该示例确定LONG字段的长度:

SET SERVEROUTPUT ON SIZE 10000;  
DECLARE
long_var LONG;
BEGIN
SELECT text_column INTO long_var
FROM table_with_long
WHERE rownum < 2;
DBMS_OUTPUT.PUT_LINE('The length is '||LENGTH(long_var));
END;

基本上,您将变量定义为LONG类型,然后选择INTO变量列.最后,它输出给用户.SET SERVEROUTPUT ON SIZE 10000允许从PUT_LINE进行假脱机以进入屏幕.

您可以使用类似的方法将LONG选择到varchar字段中.下面的示例将前2000个字符放入TABLE_B中,为了我们的目的,它有一列TEXT_FIELD:

DECLARE
   long_var LONG;
   var_var  VARCHAR2(2000);
   BEGIN
   SELECT text_column INTO long_var
   FROM table_with_long
   WHERE rownum < 2;
   var_var := substr(long_var,1,2000);
   INSERT INTO table_b
   VALUES (var_var);
   END;