求教 DATA_LENGTH与DATA_PRECISION的区别

Question

求教 DATA_LENGTH与DATA_PRECISION的区别

Answer 1

SQL> DESC EMP
Name     Type         Nullable Default Comments 
-------- ------------ -------- ------- -------- 
EMPNO    NUMBER(4)                              
ENAME    VARCHAR2(10) Y                         
JOB      VARCHAR2(9)  Y                         
MGR      NUMBER(4)    Y                         
HIREDATE DATE         Y                         
SAL      NUMBER(7,2)  Y                         
COMM     NUMBER(7,2)  Y                         
DEPTNO   NUMBER(2)    Y     SQL> select table_name,column_name,data_type,data_length,data_precision,data_scale
  2  from user_tab_columns where table_name='EMP';TABLE_NAME                     COLUMN_NAME                    DATA_TYPE                                                                        DATA_LENGTH DATA_PRECISION DATA_SCALE
------------------------------ ------------------------------ -------------------------------------------------------------------------------- ----------- -------------- ----------
EMP                            EMPNO                          NUMBER                                                                                    22              4          0
EMP                            ENAME                          VARCHAR2                                                                                  10                
EMP                            JOB                            VARCHAR2                                                                                   9                
EMP                            MGR                            NUMBER                                                                                    22              4          0
EMP                            HIREDATE                       DATE                                                                                       7                
EMP                            SAL                            NUMBER                                                                                    22              7          2
EMP                            COMM                           NUMBER                                                                                    22              7          2
EMP                            DEPTNO                         NUMBER                                                                                    22              2          08 rows selected

Answer 2

--data_length:计算表中列的数据类型存储的长度，number数据类型最大存储22字节
--关于字符串和日期的数据类型，按照具体给定的字符长度计算，如上面的ename(varchar2(10))为10个字节，
--HIREDATE DATE为7个字节；--data-precision:计算数值类型的数据类型(number,binary_float,binary_double)在数据列中的具体长度。

Answer 3

--data_length:计算表中列的数据类型存储的长度，number数据类型最大存储22字节
--关于字符串和日期的数据类型，按照具体给定的字符长度计算，如上面的ename(varchar2(10))为10个字节，
--HIREDATE DATE为7个字节；--data-precision:计算数值类型的数据类型(number,binary_float,binary_double)在数据列中的具体长度。

Answer 4

oracle data_length和data_precision的区别