1. MySQL

MySQL数据库只需要在目标字段上添加AUTO_INCREMENT，并且为表设置AUTO_INCREMENT=x。 x：自增开始的数字。

参考示例：

CREATE TABLE `dictionary` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT 'ID',
  `parent_id` int(10) unsigned NOT NULL COMMENT '父ID',
  `type` varchar(50) NOT NULL COMMENT '元数据类型',
  `item_name` varchar(100) NOT NULL COMMENT '元数据项显示名',
  `item_value` varchar(100) DEFAULT NULL COMMENT '元数据项存储值',
  `comment` varchar(200) DEFAULT NULL COMMENT '备注',
  `deleted` tinyint(1) NOT NULL DEFAULT '0' COMMENT '删除标记',
  `create_time` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP COMMENT '创建时间',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8 COMMENT='数据字典';

2. Oracle

Oracle数据库常用的设置自增字段的两种方法：

1. 创建SEQUENCE
2. IDENTITY，要求Oracle数据库版本是12c或以上

12c版本示例：

create table "dictionary" (
   "id"                 INTEGER  generated as identity ( start with 1 nocycle noorder)  not null,
   "parent_id"          INTEGER               not null,
   "type"               VARCHAR2(50)          not null,
   "item_name"          VARCHAR2(100)         not null,
   "item_value"         VARCHAR2(100),
   "comment"            VARCHAR2(200),
   "deleted"            SMALLINT             default 0  not null,
   "create_time"        TIMESTAMP            default CURRENT_TIMESTAMP  not null,
   constraint "PK_dictionary" primary key ("id")
);
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11g版本示例：

-- 建表
create table "dictionary" (
   "id"                 INTEGER               not null,
   "parent_id"          INTEGER               not null,
   "type"               VARCHAR2(50)          not null,
   "item_name"          VARCHAR2(100)         not null,
   "item_value"         VARCHAR2(100),
   "comment"            VARCHAR2(200),
   "deleted"            SMALLINT             default 0  not null,
   "create_time"        TIMESTAMP            default CURRENT_TIMESTAMP  not null,
   constraint "PK_dictionary" primary key ("id")
);
-- 创建序列
CREATE SEQUENCE DICTIONARY_ID_SEQ
INCREMENT BY 1
START WITH 1;
-- 创建触发器，非必须
CREATE OR REPLACE TRIGGER DICTIONARY_ID_SEQ_TRG
BEFORE INSERT ON "dictionary"
FOR EACH ROW
WHEN (NEW."id" IS NULL)
BEGIN
  SELECT DICTIONARY_ID_SEQ.NEXTVAL
  INTO :NEW."id"
  FROM DUAL;
END;
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3. MsSQL

MsSQL即SQL Server数据库，使用IDENTITY即可。

参考示例：

create table dictionary (
   id                   int                  identity,
   parent_id            int                  not null,
   type                 varchar(50)          not null,
   item_name            varchar(100)         not null,
   item_value           varchar(100)         null,
   comment              varchar(200)         null,
   deleted              smallint             not null default 0,
   create_time          datetime             not null default CURRENT_TIMESTAMP,
   constraint PK_dictionary primary key (id)
);