在oracle中自动增加已经创建的表

Question

如何在oracle的现有列中添加自动增量？列已经创建,它是表的主键.只想将表改为自动增量.以下是列详细信息

 Column Name         DATA_TYPE              NULLABLE
 SEQ_ID             VARCHAR2(9 BYTE)        No  

自动增量数应从150111111开始到150111112,150111113等值

谢谢

Answer 1

在11g和之前,创建一个序列以通过触发器增加列.请参阅Pre 12c版本中的自动增量主键(标识功能)

例如,

表

SQL> CREATE TABLE t (
  2    ID           NUMBER(10)    NOT NULL,
  3    text  VARCHAR2(50)  NOT NULL);

Table created.

由序列填充的PRIMARY KEY

SQL> ALTER TABLE t ADD (
  2    CONSTRAINT id_pk PRIMARY KEY (ID));

Table altered.

SEQUENCE支持主键

SQL> CREATE SEQUENCE t_seq
  2  START WITH 150111111
  3  INCREMENT BY 1;

Sequence created.

TRIGGER如果您不想在INSERT中使用序列,可以通过TRIGGER自动执行.

SQL> CREATE OR REPLACE TRIGGER t_trg
  2  BEFORE INSERT ON t
  3  FOR EACH ROW
  4  WHEN (new.id IS NULL)
  5  BEGIN
  6    SELECT t_seq.NEXTVAL
  7    INTO   :new.id
  8    FROM   dual;
  9  END;
 10  /

Trigger created.

插入

SQL> INSERT INTO t(text) VALUES('auto-increment test 1');

1 row created.

SQL> INSERT INTO t(text) VALUES('auto-increment test 2');

1 row created.

让我们看看我们是否有ID列自动递增所需的值 -

SQL> SELECT * FROM t;

        ID TEXT
---------- --------------------------------------------------
 150111111 auto-increment test 1
 150111112 auto-increment test 2

SQL>

因此,ID列现在以值150111111开始,并随后插入增加1.

在12c上,使用Identity列.请参阅Oracle 12c中的IDENTITY列自动增量功能

例如,

具有IDENTITY COLUMN的表

SQL> CREATE TABLE t
  2    (
  3      ID NUMBER GENERATED ALWAYS AS IDENTITY
  4      START WITH 150111111 INCREMENT BY 1,
  5      text VARCHAR2(50)
  6    );

Table created.

插入

SQL> INSERT INTO t
  2    ( text
  3    ) VALUES
  4    ( 'This table has an identity column'
  5    );

1 row created.

让我们看看我们是否有ID列自动递增所需的值 -

SQL> COLUMN text format A40
SQL> SELECT * FROM t;

        ID TEXT
---------- ----------------------------------------
 150111111 This table has an identity column

因此,ID列现在以值150111111开始,并随后插入增加1.

Oracle创建了一个sequence填充identity column.您可以找到它命名为ISEQ$$

SQL> SELECT sequence_name,
  2    min_value,
  3    max_value,
  4    increment_by
  5  FROM user_sequences;

SEQUENCE_NAME                   MIN_VALUE  MAX_VALUE INCREMENT_BY
------------------------------ ---------- ---------- ------------
ISEQ$$_94087                            1 1.0000E+28            1

SQL>

有关标识列的更多信息,请使用ALL_TAB_IDENTITY_COLS视图.

SQL> SELECT table_name,
  2    column_name,
  3    generation_type,
  4    identity_options
  5  FROM all_tab_identity_cols
  6  WHERE owner = 'LALIT'
  7  ORDER BY 1,
  8    2;

TABLE_NAME           COLUMN_NAME GENERATION IDENTITY_OPTIONS
-------------------- ----------- ---------- ----------------------------------------------

T                    ID          ALWAYS     START WITH: 150111111, INCREMENT BY: 1, 
                                            MAX_VALUE:9999999999999999999999999999, 
                                            MIN_VALUE: 1, CYCLE_FLAG: N, CACHE_SIZE: 20, 
                                            ORDER_FLAG: N