读取long类型数据

CREATE OR REPLACE FUNCTION LONG_TO_CHAR(uTABLE IN VARCHAR2,uID IN NUMBER)
RETURN VARCHAR2
AS
  uVal VARCHAR2(32767); 
BEGIN
  SELECT DATA_DEFAULT INTO uVal FROM USER_TAB_COLS WHERE TABLE_NAME = UPPER(uTABLE) AND COLUMN_ID = uID;
  uVal := SUBSTR(uVal,1,50); 
  RETURN uVal;  
END LONG_TO_CHAR;

　　创建了以后，就可以调用之了

--在第一行和最后一行改表名             查询表结构
SELECT 'TABLEA'  as 表名, A.COLUMN_NAME as 字段,
                           case
                             when A.DATA_TYPE = 'NUMBER' and A.DATA_PRECISION IS NULL AND a.DATA_SCALE = 0 then
                              'INTEGER'
                             when A.DATA_TYPE = 'TIMESTAMP(6)'then
                              'TIMESTAMP'
                             else
                               A.DATA_TYPE
                           END as 数据类型,
                           case
                             when A.DATA_TYPE in ('CHAR','NCHAR') then
                              to_char(A.CHAR_COL_DECL_LENGTH)
                             when A.DATA_TYPE in ('VARCHAR2','NVARCHAR2'，'RAW','UROWID') then
                              to_char(A.CHAR_LENGTH)
                             when A.DATA_TYPE = 'FLOAT' then
                              to_char(A.DATA_PRECISION)
                             when A.DATA_TYPE = 'NUMBER' and A.DATA_PRECISION IS NULL AND a.DATA_SCALE = 0 then
                              ''
                             when A.DATA_TYPE = 'NUMBER' AND a.DATA_SCALE = 0 then
                              to_char(A.DATA_PRECISION)
                             when A.DATA_TYPE = 'NUMBER' AND a.DATA_SCALE != 0 then
                              to_char(A.DATA_PRECISION || ',' || A.DATA_SCALE)
                             when A.DATA_TYPE = 'TIMESTAMP(6)' then
                              '6'
                              ELSE
                               ''
                           END as 长度,
                           decode(A.NULLABLE,'Y',null,'N','N') AS 可为空,
                           LONG_TO_CHAR(A.TABLE_NAME,A.COLUMN_ID) as 默认值, 
                           B.comments as 备注
                           
                           
                      from sys.user_tab_cols A
                      left join sys.user_col_comments B on A.TABLE_NAME = B.table_name
                       and A.COLUMN_NAME = B.column_name

                                where A.TABLE_NAME = 'TABLEA'
                                order by A.TABLE_NAME, A.COLUMN_ID

　　

一段时间后，又发现了新问题，我想获得user_constraints表中的search_condition信息，但这是视图中的一个字段，不能使用上面调用的方法

于是重新写了一个

create or replace function search_cond( p_cons_name in varchar2 ) return varchar2
as
l_search_condition varchar2(4000);
begin
select SEARCH_CONDITION into l_search_condition
from user_constraints
where constraint_name = p_cons_name;

return l_search_condition;
end;