建表语句
declare
v_sql varchar2(32767) ;
begin
v_sql := 'create table test ( ' ;
for i in 1..500 loop
v_sql := v_sql || 'name'||i||' varchar2(2000) ,' ;
end loop ;
v_sql := substr(v_sql,1,length(v_sql)-1) ;
v_sql := v_sql || ');' ;
dbms_output.put_line(v_sql) ;
end ;
复制粘贴创建表
_dex@david> desc test
name null? type
----------------------------------------------------- -------- ------------------------------------
name1 varchar2(2000)
name2 varchar2(2000)
name3 varchar2(2000)
.....
name500 varchar2(2000)
_dex@david> insert into test (name500) values (lpad(1,300,'d')) ;
1 row created.
_dex@david> select
2 length(t.name500),
3 dbms_rowid.rowid_relative_fno(t.rowid) as fno#,
4 dbms_rowid.rowid_block_number(t.rowid) as blk#,
5 dbms_rowid.rowid_row_number(t.rowid) as row#
6 from dex.test t
7 /
length(t.name500) fno# blk# row#
----------------- ---------- ---------- ----------
300 4 925 1
1 4 925 3
300 4 925 5
使用bbed查看
首先看row#为1长度为300的数据
bbed> set dba 4,925
dba 0x0100039d (16778141 4,925)
bbed> p kdbr
sb2 kdbr[0] @142 7504
sb2 kdbr[1] @144 7250
sb2 kdbr[2] @146 6991
sb2 kdbr[3] @148 6737
sb2 kdbr[4] @150 6177
sb2 kdbr[5] @152 5923
bbed> p *kdbr[1]
rowdata[1327]
-------------
ub1 rowdata[1327] @7374 0x28
bbed> dump /v offset 7374 count 128
file: /u01/apps/oracle/oradata/david/users01.dbf (4)
block: 925 offsets: 7374 to 7501 dba:0x0100039d
-------------------------------------------------------
2801f501 00039d00 00ffffff ffffffff l (.õ.............
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
ffffffff ffffffff ffffffff ffffffff l ................
这些是row piece header
2801f501 00039d00 00
1个字节的flag=28
16进制28=二进制00101000=--h-f---=head of rowpiece + first data piece
1个字节的lb（itl slot)=01
1个字节的cc column count=f5=245 （因为最后一列name500不为空，所以null都需要使用ff来表示，也就是说需要存储500列的数据）