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。以下是专栏详情

 Column Name         DATA_TYPE              NULLABLE
 SEQ_ID             VARCHAR2(9 BYTE)        No  

自动增量编号应从150111111开始到150111112,150111113等值

由于

Answer 1

在 11g 之前，创建序列以通过触发器增加列。见Auto-increment primary key in Pre 12c releases (Identity functionality)

例如，

表格

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

Table created.

PRIMARY KEY 将由序列

填充

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 中输入序列，可以通过TRIGGER自动执行此序列。

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，使用标识列。请参阅 IDENTITY column autoincrement functionality in Oracle 12c

例如，

带 IDENTITY COLUMN的

TABLE

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sequence来填充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