ORACLE字段存储长度与定义长度不一致

Question

为什么这个数据库里面DESC出来的表结构跟all_tab_columns里面不一样

Answer 1

解析（analysis）一下这个表试试，数据字典是根据系统解析的结构生成的；
而你desc得到的应该是准确的

Answer 2

你的Oracle字符集，是不是采用的中文或者是宽字符集？我使用的US7ASCII，没有类似问题，估计是中文之类字符集造成的。

Answer 3

all_tab_columns 里面有个DATA_LENGTH字段你看看

Answer 4

SYS@anqing2(rac2)> desc t1
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 OWNER                                              VARCHAR2(30)
 OBJECT_NAME                                        VARCHAR2(128)
 SUBOBJECT_NAME                                     VARCHAR2(30)
 OBJECT_ID                                          NUMBER
 DATA_OBJECT_ID                                     NUMBER
 OBJECT_TYPE                                        VARCHAR2(19)
 CREATED                                            DATE
 LAST_DDL_TIME                                      DATE
 TIMESTAMP                                          VARCHAR2(19)
 STATUS                                             VARCHAR2(7)
 TEMPORARY                                          VARCHAR2(1)
 GENERATED                                          VARCHAR2(1)
 SECONDARY                                          VARCHAR2(1)SYS@anqing2(rac2)> select COLUMN_NAME,DATA_LENGTH from all_tab_columns where table_name='T1'; COLUMN_NAME                    DATA_LENGTH
------------------------------ -----------
OWNER                                   30
OBJECT_NAME                            128
SUBOBJECT_NAME                          30
OBJECT_ID                               22
DATA_OBJECT_ID                          22
OBJECT_TYPE                             19
CREATED                                  7
LAST_DDL_TIME                            7
TIMESTAMP                               19
STATUS                                   7
TEMPORARY                                1COLUMN_NAME                    DATA_LENGTH
------------------------------ -----------
GENERATED                                1
SECONDARY                                113 rows selected.
理论上不一行出现这样的问题。 不过通过你贴的数据看，正好相差3倍。在查询之前指定下字符集，在查询看看。