原创作品，出自 “深蓝的blog” 博客，欢迎转载，转载时请务必注明出处，否则追究版权法律责任。
深蓝的blog：http://blog.csdn.net/huangyanlong/article/details/45854385
今天在为某系统数据库结构整理升级脚本时，遇到了“命名字节过长的错误”，类似于下面的截图语句：
由于升级的结构中对于字段名的命名根据业务进行了修改，出现了命名过长的情况。
这里想说一下，对于oracle，表名、字段名等对象命名字节个数限制在了30个字节！是无法更改的，这是oracle的固化设置。
我们可以通过查看数据库字典进一步验证一下。
实验:
在sys用户下，查看user_tables这个视图，可以发现在table_name这个字段，类型为varchar，长度为30，如下：
再进一步查看视图的结构，如下：
create or replace view user_tables
(table_name, tablespace_name, cluster_name, iot_name, status, pct_free, pct_used, ini_trans, max_trans, initial_extent, next_extent, min_extents, max_extents, pct_increase, freelists, freelist_groups, logging, backed_up, num_rows, blocks, empty_blocks, avg_space, chain_cnt, avg_row_len, avg_space_freelist_blocks, num_freelist_blocks, degree, instances, cache, table_lock, sample_size, last_analyzed, partitioned, iot_type, temporary, secondary, nested, buffer_pool, flash_cache, cell_flash_cache, row_movement, global_stats, user_stats, duration, skip_corrupt, monitoring, cluster_owner, dependencies, compression, compress_for, dropped, read_only, segment_created, result_cache)
as
select o.name,
decode(bitand(t.property,2151678048), 0, ts.name,
decode(t.ts#, 0, null, ts.name)),
decode(bitand(t.property, 1024), 0, null, co.name),
decode((bitand(t.property, 512)+bitand(t.flags, 536870912)),
0, null, co.name),
decode(bitand(t.trigflag, 1073741824), 1073741824, 'UNUSABLE', 'VALID'),
decode(bitand(t.property, 32+64), 0, mod(t.pctfree$, 100), 64, 0, null),
decode(bitand(ts.flags, 32), 32, to_number(NULL),
decode(bitand(t.property, 32+64), 0, t.pctused$, 64, 0, null)),
decode(bitand(t.property, 32), 0, t.initrans, null),
decode(bitand(t.property, 32), 0, t.maxtrans, null),
decode(bitand(t.property, 17179869184), 17179869184,
ds.initial_stg * ts.blocksize,
s.iniexts * ts.blocksize),
decode(bitand(t.property, 17179869184), 17179869184,
ds.next_stg * ts.blocksize,
s.extsize * ts.blocksize),
decode(bitand(t.property, 17179869184), 17179869184,
ds.minext_stg, s.minexts),
decode(bitand(t.property, 17179869184), 17179869184,
ds.maxext_stg, s.maxexts),
decode(bitand(ts.flags, 3), 1, to_number(NULL),
decode(bitand(t.property, 17179869184), 17179869184,
ds.pctinc_stg, s.extpct)),
decode(bitand(ts.flags, 32), 32, to_number(NULL),
decode(bitand(o.flags, 2), 2, 1,
decode(bitand(t.property, 17179869184), 17179869184,
ds.frlins_stg, decode(s.lists, 0, 1, s.lists)))),
decode(bitand(ts.flags, 32), 32, to_number(NULL),
decode(bitand(o.flags, 2), 2, 1,
decode(bitand(t.property, 17179869184), 17179869184,
ds.maxins_stg, decode(s.groups, 0, 1, s.groups)))),
decode(bitand(t.property, 32+64), 0,
decode(bitand(t.flags, 32), 0, 'YES', 'NO'), null),
decode(bitand(t.flags,1), 0, 'Y', 1, 'N', '?'),
t.rowcnt,
decode(bitand(t.property, 64), 0, t.blkcnt, null),
decode(bitand(t.property, 64), 0, t.empcnt, null),
decode(bitand(t.property, 64), 0, t.avgspc, null),
t.chncnt, t.avgrln, t.avgspc_flb,
decode(bitand(t.property, 64), 0, t.flbcnt, null),
lpad(decode(t.degree, 32767, 'DEFAULT', nvl(t.degree,1)),10),
lpad(decode(t.instances, 32767, 'DEFAULT', nvl(t.instances,1)),10),
lpad(decode(bitand(t.flags, 8), 8, 'Y', 'N'),5),
decode(bitand(t.flags, 6), 0, 'ENABLED', 'DISABLED'),
t.samplesize, t.analyzetime,
decode(bitand(t.property, 32), 32, 'YES', 'NO'),
decode(bitand(t.property, 64), 64, 'IOT',
decode(bitand(t.property, 512), 512, 'IOT_OVERFLOW',
decode(bitand(t.flags, 536870912), 536870912, 'IOT_MAPPING', null))),
decode(bitand(o.flags, 2), 0, 'N', 2, 'Y', 'N'),
decode(bitand(o.flags, 16), 0, 'N', 16, 'Y', 'N'),
decode(bitand(t.property, 8192), 8192, 'YES',
decode(bitand(t.property, 1), 0, 'NO', 'YES')),
decode(bitand(o.flags, 2), 2, 'DEFAULT',
decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,
ds.bfp_stg, s.cachehint), 3),
1, 'KEEP', 2, 'RECYCLE', 'DEFAULT')),
decode(bitand(o.flags, 2), 2, 'DEFAULT',
decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,
ds.bfp_stg, s.cachehint), 12)/4,
1, 'KEEP', 2, 'NONE', 'DEFAULT')),
decode(bitand(o.flags, 2), 2, 'DEFAULT',
decode(bitand(decode(bitand(t.property, 17179869184), 17179869184,
ds.bfp_stg, s.cachehint), 48)/16,
1, 'KEEP', 2, 'NONE', 'DEFAULT')),
decode(bitand(t.flags, 131072), 131072, 'ENABLED', 'DISABLED'),
decode(bitand(t.flags, 512), 0, 'NO', 'YES'),
decode(bitand(t.flags, 256), 0, 'NO', 'YES'),
decode(bitand(o.flags, 2), 0, NULL,
decode(bitand(t.property, 8388608), 8388608,
'SYS$SESSION', 'SYS$TRANSACTION')),
decode(bitand(t.flags, 1024), 1024, 'ENABLED', 'DISABLED'),
decode(bitand(o.flags, 2), 2, 'NO',
decode(bitand(t.property, 2147483648), 2147483648, 'NO',
decode(ksppcv.ksppstvl, 'TRUE', 'YES', 'NO'))),
decode(bitand(t.property, 1024), 0, null, cu.name),
decode(bitand(t.flags, 8388608), 8388608, 'ENABLED', 'DISABLED'),
case when (bitand(t.property, 32) = 32) then
null
when (bitand(t.property, 17179869184) = 17179869184) then
decode(bitand(ds.flags_stg, 4), 4, 'ENABLED', 'DISABLED')
else
decode(bitand(s.spare1, 2048), 2048, 'ENABLED', 'DISABLED')
end,
case when (bitand(t.property, 32) = 32) then
null
when (bitand(t.property, 17179869184) = 17179869184) then
decode(bitand(ds.flags_stg, 4), 4,
case when bitand(ds.cmpflag_stg, 3) = 1 then 'BASIC'
when bitand(ds.cmpflag_stg, 3) = 2 then 'OLTP'
else decode(ds.cmplvl_stg, 1, 'QUERY LOW',
2, 'QUERY HIGH',
3, 'ARCHIVE LOW',
'ARCHIVE HIGH') end,
null)
else
decode(bitand(s.spare1, 2048), 0, null,
case when bitand(s.spare1, 16777216) = 16777216 -- 0x1000000
then 'OLTP'
when bitand(s.spare1, 100663296) = 33554432 -- 0x2000000
then 'QUERY LOW'
when bitand(s.spare1, 100663296) = 67108864 -- 0x4000000
then 'QUERY HIGH'
when bitand(s.spare1, 100663296) = 100663296 -- 0x2000000+0x4000000
then 'ARCHIVE LOW'
when bitand(s.spare1, 134217728) = 134217728 -- 0x8000000
then 'ARCHIVE HIGH'
else 'BASIC' end)
end,
decode(bitand(o.flags, 128), 128, 'YES', 'NO'),
decode(bitand(t.trigflag, 2097152), 2097152, 'YES', 'NO'),
decode(bitand(t.property, 17179869184), 17179869184, 'NO',
decode(bitand(t.property, 32), 32, 'N/A', 'YES')),
decode(bitand(t.property,16492674416640),2199023255552,'FORCE',
4398046511104,'MANUAL','DEFAULT')
from sys.ts$ ts, sys.seg$ s, sys.obj$ co, sys.tab$ t, sys.obj$ o,
sys.deferred_stg$ ds, sys.obj$ cx, sys.user$ cu, x$ksppcv ksppcv,
x$ksppi ksppi
where o.owner# = userenv('SCHEMAID')
and o.obj# = t.obj#
and bitand(t.property, 1) = 0
and bitand(o.flags, 128) = 0
and t.bobj# = co.obj# (+)
and t.ts# = ts.ts#
and t.file# = s.file# (+)
and t.block# = s.block# (+)
and t.ts# = s.ts# (+)
and t.obj# = ds.obj# (+)
and t.dataobj# = cx.obj# (+)
and cx.owner# = cu.user# (+)
and ksppi.indx = ksppcv.indx
and ksppi.ksppinm = '_dml_monitoring_enabled'
;
comment on table USER_TABLES is 'Description of the user''s own relational tables';
comment on column USER_TABLES.TABLE_NAME is 'Name of the table';
comment on column USER_TABLES.TABLESPACE_NAME is 'Name of the tablespace containing the table';
comment on column USER_TABLES.CLUSTER_NAME is 'Name of the cluster, if any, to which the table belongs';
comment on column USER_TABLES.IOT_NAME is 'Name of the index-only table, if any, to which the overflow or mapping table entry belongs';
comment on column USER_TABLES.STATUS is 'Status of the table will be UNUSABLE if a previous DROP TABLE operation failed,
VALID otherwise';
comment on column USER_TABLES.PCT_FREE is 'Minimum percentage of free space in a block';
comment on column USER_TABLES.PCT_USED is 'Minimum percentage of used space in a block';
comment on column USER_TABLES.INI_TRANS is 'Initial number of transactions';
comment on column USER_TABLES.MAX_TRANS is 'Maximum number of transactions';
comment on column USER_TABLES.INITIAL_EXTENT is 'Size of the initial extent in bytes';
comment on column USER_TABLES.NEXT_EXTENT is 'Size of secondary extents in bytes';
comment on column USER_TABLES.MIN_EXTENTS is 'Minimum number of extents allowed in the segment';
comment on column USER_TABLES.MAX_EXTENTS is 'Maximum number of extents allowed in the segment';
comment on column USER_TABLES.PCT_INCREASE is 'Percentage increase in extent size';
comment on column USER_TABLES.FREELISTS is 'Number of process freelists allocated in this segment';
comment on column USER_TABLES.FREELIST_GROUPS is 'Number of freelist groups allocated in this segment';
comment on column USER_TABLES.LOGGING is 'Logging attribute';
comment on column USER_TABLES.BACKED_UP is 'Has table been backed up since last modification?';
comment on column USER_TABLES.NUM_ROWS is 'The number of rows in the table';
comment on column USER_TABLES.BLOCKS is 'The number of used blocks in the table';
comment on column USER_TABLES.EMPTY_BLOCKS is 'The number of empty (never used) blocks in the table';
comment on column USER_TABLES.AVG_SPACE is 'The average available free space in the table';
comment on column USER_TABLES.CHAIN_CNT is 'The number of chained rows in the table';
comment on column USER_TABLES.AVG_ROW_LEN is 'The average row length, including row overhead';
comment on column USER_TABLES.AVG_SPACE_FREELIST_BLOCKS is 'The average freespace of all blocks on a freelist';
comment on column USER_TABLES.NUM_FREELIST_BLOCKS is 'The number of blocks on the freelist';
comment on column USER_TABLES.DEGREE is 'The number of threads per instance for scanning the table';
comment on column USER_TABLES.INSTANCES is 'The number of instances across which the table is to be scanned';
comment on column USER_TABLES.CACHE is 'Whether the table is to be cached in the buffer cache';
comment on column USER_TABLES.TABLE_LOCK is 'Whether table locking is enabled or disabled';
comment on column USER_TABLES.SAMPLE_SIZE is 'The sample size used in analyzing this table';
comment on column USER_TABLES.LAST_ANALYZED is 'The date of the most recent time this table was analyzed';
comment on column USER_TABLES.PARTITIONED is 'Is this table partitioned? YES or NO';
comment on column USER_TABLES.IOT_TYPE is 'If index-only table, then IOT_TYPE is IOT or IOT_OVERFLOW or IOT_MAPPING else NULL';
comment on column USER_TABLES.TEMPORARY is 'Can the current session only see data that it place in this object itself?';
comment on column USER_TABLES.SECONDARY is 'Is this table object created as part of icreate for domain indexes?';
comment on column USER_TABLES.NESTED is 'Is the table a nested table?';
comment on column USER_TABLES.BUFFER_POOL is 'The default buffer pool to be used for table blocks';
comment on column USER_TABLES.FLASH_CACHE is 'The default flash cache hint to be used for table blocks';
comment on column USER_TABLES.CELL_FLASH_CACHE is 'The default cell flash cache hint to be used for table blocks';
comment on column USER_TABLES.ROW_MOVEMENT is 'Whether partitioned row movement is enabled or disabled';
comment on column USER_TABLES.GLOBAL_STATS is 'Are the statistics calculated without merging underlying partitions?';
comment on column USER_TABLES.USER_STATS is 'Were the statistics entered directly by the user?';
comment on column USER_TABLES.DURATION is 'If temporary table, then duration is sys$session or sys$transaction else NULL';
comment on column USER_TABLES.SKIP_CORRUPT is 'Whether skip corrupt blocks is enabled or disabled';
comment on column USER_TABLES.MONITORING is 'Should we keep track of the amount of modification?';
comment on column USER_TABLES.CLUSTER_OWNER is 'Owner of the cluster, if any, to which the table belongs';
comment on column USER_TABLES.DEPENDENCIES is 'Should we keep track of row level dependencies?';
comment on column USER_TABLES.COMPRESSION is 'Whether table compression is enabled or not';
comment on column USER_TABLES.COMPRESS_FOR is 'Compress what kind of operations';
comment on column USER_TABLES.DROPPED is 'Whether table is dropped and is in Recycle Bin';
comment on column USER_TABLES.READ_ONLY is 'Whether table is read only or not';
comment on column USER_TABLES.SEGMENT_CREATED is 'Whether the table segment is created or not';
comment on column USER_TABLES.RESULT_CACHE is 'The result cache mode annotation for the table';
我们可以由视图结构中锁定到三个地方，定位到来源，如下：
table_name
o.name
sys.obj$ o
可以发现，table_name字段来源于sys.obj$中的name字段，如下：
我们尝试修改一下sys.obj$中name字段的长度，如下：
可以看到，我们是无法修改数据库系统的字典字段的定义。用同样的方法，我们还可以查看USER_TAB_COLUMNS,USER_CONSTRAINTS等视图，会发现对于oracle，限制了命名的长度，都限制在了30个字节。
之后在网上搜了一下，发现对于不同的数据库原来命名长度限制是不一样的，摘录如下：
|
数据库 |
表名长度限制 |
字段名长度限制 |
|
oracle |
30 |
30 |
|
mysql |
64 |
64 |
|
db2 |
128 |
128 |
|
access |
64 |
64 |
|
sqlserver |
128 |
128 |
原创作品，出自 “深蓝的blog” 博客，欢迎转载，转载时请务必注明出处，否则追究版权法律责任。
深蓝的blog：http://blog.csdn.net/huangyanlong/article/details/45854385
原文地址：http://blog.csdn.net/huangyanlong/article/details/45854385
