来自Thomas Kyte 《Oracle9i/10g/11g编程艺术》 12章节中.由于long的操作限制,那么在操作long之前可以将该类型的结果转换为varchar2然后再使用,long_help.substr_of的基本意思是将long结果的的前4000字节转换为varchar2类型.如果long的数据超过了4000字节,那么可以将循环调用此函数
create or replace package long_help
authid current_user
as
function substr_of
( p_query in varchar2,
p_from in number,
p_for in number,
p_name1 in varchar2 default NULL,
p_bind1 in varchar2 default NULL,
p_name2 in varchar2 default NULL,
p_bind2 in varchar2 default NULL,
p_name3 in varchar2 default NULL,
p_bind3 in varchar2 default NULL,
p_name4 in varchar2 default NULL,
p_bind4 in varchar2 default NULL )
return varchar2;
end;
create or replace package body long_help
as
g_cursor number := dbms_sql.open_cursor;
g_query varchar2(32765);
procedure bind_variable( p_name in varchar2, p_value in varchar2 )
is
begin
if ( p_name is not null )
then
dbms_sql.bind_variable( g_cursor, p_name, p_value );
end if;
end;
function substr_of
( p_query in varchar2,
p_from in number,
p_for in number,
p_name1 in varchar2 default NULL,
p_bind1 in varchar2 default NULL,
p_name2 in varchar2 default NULL,
p_bind2 in varchar2 default NULL,
p_name3 in varchar2 default NULL,
p_bind3 in varchar2 default NULL,
p_name4 in varchar2 default NULL,
p_bind4 in varchar2 default NULL )
return varchar2
as
l_buffer varchar2(4000);
l_buffer_len number;
begin
if ( nvl(p_from,0) <= 0 )
then
raise_application_error
(-20002, 'From must be >= 1 (positive numbers)' );
end if;
if ( nvl(p_for,0) not between 1 and 4000 )
then
raise_application_error
(-20003, 'For must be between 1 and 4000' );
end if;
if ( p_query <> g_query or g_query is NULL )
then
if ( upper(trim(nvl(p_query,'x'))) not like 'SELECT%')
then
raise_application_error
(-20001, 'This must be a select only' );
end if;
dbms_sql.parse( g_cursor, p_query, dbms_sql.native );
g_query := p_query;
end if;
bind_variable( p_name1, p_bind1 );
bind_variable( p_name2, p_bind2 );
bind_variable( p_name3, p_bind3 );
bind_variable( p_name4, p_bind4 );
dbms_sql.define_column_long(g_cursor, 1);
if (dbms_sql.execute_and_fetch(g_cursor)>0)
then
dbms_sql.column_value_long
(g_cursor, 1, p_for, p_from-1,
l_buffer, l_buffer_len );
end if;
return l_buffer;
end substr_of;
end;
使用方法:查询DBA_TAB_PARTITIONS中的HIGH_VALUE
SELECT *
FROM (SELECT TABLE_OWNER,
TABLE_NAME,
PARTITION_NAME,
LONG_HELP.SUBSTR_OF('SELECT HIGH_VALUE
FROM DBA_TAB_PARTITIONS WHERE TABLE_OWNER=:TABLE_OWNER
AND TABLE_NAME=:TABLE_NAME
AND PARTITION_NAME=:PARTITION_NAME',
1,
4000,
'TABLE_OWNER',
TABLE_OWNER,
'TABLE_NAME',
TABLE_NAME,
'PARTITION_NAME',
PARTITION_NAME) HIGH_VALUE
FROM DBA_TAB_PARTITIONS);
