方法一、使用add constraint 方法添加主键约束 alter table 表名 add constraint 主键名 primary key (列名1,列名2,...) 方法二、使用索引创建主键 (和方法一没有区别,可以将方法一理解为省略了using index) alter table 表名 add constraint 主键名 primary key (列名1,列名2,...) using index [index_name...
As discussed in the documentation, a sequence in Oracle prevents duplicate values from being created simultaneously because multiple users are effectively forced to “take turns” before each sequential item is generated. For the purposes of creating a unique primary key for a new table, first we ...
http://stackoverflow.com/questions/4668146/how-to-add-a-primary-key-on-a-oracle-view It allows them, but only in a disabled state. They provide information to the optimiser but cannot be enforced. –Tony AndrewsJan 12 '11 at 12:55 Exactly what Tony said. And some tools that do object...
when the system variable 'sql_require_primary_key' is set.Add a primary key to the table or unset this variable to avoid this message.Note that tables without a primary key can cause performance problems in row-based replication,so p...
可见,mysql的key是同时具有constraint和index的意义,这点和其他数据库表现的可能有区别。 (至少在oracle上建立外键,不会自动建立index),因此创建key也有如下几种方式: (1)在字段级以key方式建立, 如 create table t (id int not null primary key);
SQL> ALTER TABLE larry_test ADD CONSTRAINT pk_larry_test PRIMARY KEY (terminal_id)USING INDEX TABLESPACE indx; Table altered. 当然如果再灵活些,还可以指定索引的存储参数等等。 同时还有两个小问题: 首先我们都知道所谓主键就是,该字段或多个字段上为唯一(unique)索引且字段不为空。
add constraint AK_AccountName --约束名 unique (Account_Name) -- 列名 3、主键约束(非空且唯一)primary key 只允许一个主键,主键可以是单个字段或多字段的组合(联合主键),Oracle会自动为主键字段创建对应的唯一性索引。主键约束既可以在字段级定义、也可以在表级定义。
To make an Oracle autoincrement column in DeZign for Databases: Select Dictionary | Sequences from the application menu. In the Sequences dialog, add a new sequence (let's say Sequence_1). Press OK to save your changes. Go to the Entity dialog of the entity which owns the Attribute...
可见,mysql的key是同时具有constraint和index的意义,这点和其他数据库表现的可能有区别。 (至少在Oracle上建立外键,不会自动建立index),因此创建key也有如下几种方式: (1)在字段级以key方式建立, 如 create table t (id int not null primary key);
Add Primary Key while Creating a Table The syntax is below: CREATE TABLE SCHEMA_NAME.TABLE_NAME ( COLUMN1 datatype [ NULL | NOT NULL ] PRIMARY KEY, COLUMN2 datatype [ NULL | NOT NULL ], ... ); Let’s create a table namedEmployeesin theHumanResourcesschema for testing purposes with ...