Oracle使用虚拟列创建表

Question

我在Oracle（Oracle数据库11g企业版11.1.0.7.0版-64位生产）上运行此SQL：

CREATE TABLE R_SEQUENCES_COUNT1
  (
    DS_ID NUMBER,
    LINE_TIME TIMESTAMP(6),
    DAY_ID  DATE GENERATED ALWAYS   AS (TRUNC(LINE_TIME)),
    HOUR_ID  DATE GENERATED ALWAYS  AS (TRUNC(LINE_TIME,'HH24')) ,
    MINUTE_ID DATE GENERATED ALWAYS AS (TRUNC(LINE_TIME,'MI')) ,
    SECOND_ID DATE GENERATED ALWAYS AS (LINE_TIME),
    R_ID       NUMBER,
    SEQUENCE_ID NUMBER
  )NOLOGGING
  TABLESPACE TWC_DATA_SPACE
  PARTITION BY LIST (DS_ID)
  SUBPARTITION BY LIST(DAY_ID)
  (PARTITION DS_ID_OTHER VALUES (DEFAULT) 
  (SUBPARTITION DS_ID_OTHER_DAY_ID_OTHER VALUES (DEFAULT)))

并得到这个错误：

Error at Command Line:8 Column:40
Error report:
SQL Error: ORA-54016: Invalid column expression was specified

怎么了？

Answer 1

根据需要将其用作日期，请使用：

SECOND_ID DATE GENERATED ALWAYS AS (cast(LINE_TIME as date)),

否则你可以做：

SECOND_ID TIMESTAMP GENERATED ALWAYS AS (LINE_TIME + numtodsinterval(0, 'day')),

但是在那种情况下，不确定为什么要使用该列的确切副本？

例如第二个：

SQL> CREATE TABLE R_SEQUENCES_COUNT1
  2    (
  3      DS_ID NUMBER,
  4      LINE_TIME TIMESTAMP(6),
  5      DAY_ID  DATE GENERATED ALWAYS   AS (TRUNC(LINE_TIME)),
  6      HOUR_ID  DATE GENERATED ALWAYS  AS (TRUNC(LINE_TIME,'HH24')) ,
  7      MINUTE_ID DATE GENERATED ALWAYS AS (TRUNC(LINE_TIME,'MI')) ,
  8      SECOND_ID TIMESTAMP GENERATED ALWAYS AS (LINE_TIME+numtodsinterval(0, 'day')),
  9      R_ID       NUMBER,
 10      SEQUENCE_ID NUMBER
 11    )NOLOGGING
 12  /

Table created.

SQL> insert into  R_SEQUENCES_COUNT1 (ds_id, line_time) values (1, systimestamp);

1 row created.

SQL> @print_Table "select * from  R_SEQUENCES_COUNT1"
DS_ID                         : 1
LINE_TIME                     : 14-mar-2013 09:56:31.104921
DAY_ID                        : 14-mar-2013 00:00:00
HOUR_ID                       : 14-mar-2013 09:00:00
MINUTE_ID                     : 14-mar-2013 09:56:00
SECOND_ID                     : 14-mar-2013 09:56:31.104921
R_ID                          :
SEQUENCE_ID                   :
-----------------

Answer 2

在您的创作中

//set condition is invalid
SECOND_ID DATE GENERATED ALWAYS AS (LINE_TIME)



// change to this...
SECOND_ID DATE GENERATED ALWAYS AS (TIMESTAMP)

数据类型TIMESTAMP允许几分之一秒。 如果将其转换为DATE，则小数秒将被删除-例如

所以在选择第二个..

select cast(systimestamp as date) from dual;

我认为的另一种方式是...

是将时间戳记TRUNC()为秒，您可以将其转换为日期

CAST( timestamp AS DATE)

然后像这样执行TRUNC：

TRUNC(CAST(timestamp AS DATE), 'YEAR')