oracle的长度限制

一. varchar2长度限制问题

1) 表字段创建最大长度：4000
SQL> CREATE TABLE t_test1(a VARCHAR2( 4000 )); --正确
Table created.
SQL> CREATE TABLE t_test2(a VARCHAR2( 4001 )); --错误
CREATE TABLE t_test2(a VARCHAR2(4001))
*
ERROR at line 1:
ORA-00910: specified length too long for its datatype


2) plsql变量定义最大长度：32767
SQL> CREATE OR REPLACE PROCEDURE sp_test1 (p IN VARCHAR2 DEFAULT NULL ) --正确
IS
x_var VARCHAR2 ( 32767 );
BEGIN
DBMS_OUTPUT.put_line (p);
END;
/
Procedure created.
SQL> CREATE OR REPLACE PROCEDURE sp_test2 (p IN VARCHAR2 DEFAULT NULL ) --错误
IS
x_var2 VARCHAR2 ( 32768 );
BEGIN
NULL;
END;
/
Warning: Procedure created with compilation errors.
SQL> show error;
Errors for PROCEDURE SP_TEST2:
LINE/COL ERROR
-------- -----------------------------------------------------------------
3/23 PLS-00215: String length constraints must be in range (1 ..
32767)

3) plsql调用参数最大长度：65535
SQL> DECLARE
lv_test VARCHAR2 (32767);
BEGIN
FOR i IN 1 .. 32767
LOOP
lv_test := lv_test || '-';
END LOOP; 
sp_test1 (LENGTHB (lv_test || lv_test || ' 1 '));
END;
/
65535
SQL> DECLARE
lv_test VARCHAR2 (32767);
BEGIN
FOR i IN 1 .. 32767
LOOP
lv_test := lv_test || '-';
END LOOP;
sp_test1 (LENGTHB (lv_test || lv_test || ' 12 '));
END;
/
DECLARE
*
ERROR at line 1:
ORA-06502: PL/SQL: numeric or value error: character string buffer too small
ORA-06512: at line 9

二. dbms_output.put_line长度限制问题

对于10g以上版本(包括10g), dbms_output.put_line的最大长度限制是 32767 . 如果报错buffer overflow, 执行如下语句即可:
set serveroutput ON SIZE UNLIMITED FORMAT WORD_WRAPPED

对于10g以下版本dbms_output.put_line最大长度限制是 255 .

oracle表名、字段名等对象的命名长度限制

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。先思考一下，哪里可以获得关于这类命名的信息呢？有没有想到USER_TAB_COLUMNS,USER_CONSTRAINTS这一类的视图。我们来做一个验证。

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，这里记录的表的名称，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