long查询结果转换为varchar2类型
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
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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
;
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使用方法:查询DBA_TAB_PARTITIONS中的HIGH_VALUE
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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);
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