1.主键约束:列被约束为(非空、不重复) 格式:alter table 表格名称 add constraint 约束名称 primary key (列名) 例子:alter table emp add constraint ppp primary key (id); 2.外键约束:列被约束为引用其他表的主键 格式:alter table 表名 add constraint 约束名称 foreign key (列名) references 被引用的表...
oracle add constraint用法 Oracle中使用ADD CONSTRAINT语句来添加约束。具体用法如下：1.添加主键约束：ALTER TABLE table_name ADD CONSTRAINT pk_constraint PRIMARY KEY (column1, column2, ...);2.添加唯一约束：ALTER TABLE table_name ADD CONSTRAINT unique_constraint UNIQUE (column1, column2, ...);3....
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...
sql ALTER TABLE table_name ADD (column_definition | constraint_definition) [, ...]; 2. 约束(CONSTRAINT)的概念及其在数据库中的作用 约束是数据库中的一种规则,用于限制表中数据的类型和取值范围,以确保数据的完整性和一致性。常见的约束类型包括主键约束(PRIMARY KEY)、唯一约束(UNIQUE)、外键约束(FOREIG...
Somewhere I think I’ve published a note that points out that when you add a primary key constraint Oracle first checks that the key column (or column set) is not null[update Jan 2016: couldn’t find it, so finallygot around to writing it(again)]– which means that adding a primary ...
问SQL_Add约束并使用LIKE检查字符串EN使用外键约束 --（1）、在字段后使用 references...
DEFERABLE: allow deferred, but no deferred right now. It is assgined only when create this constraint. INITIAL DEFERED/IMMEDIATE: deferable in advance, initial deferred => DEFERRED(above) initial immediate => NO DEFERRED(above) alter session set constraints=immediate/deferred; ...
You can add acolumn with a NOT NULL constraint only if the table does notcontain any rows, or you specify a default value. --我们仅可以在表中没有记录或者指定默认值的情况下才可以使用NOT NULL 限制。 1.3 说明 通过上面的说明,对add column 有了一定的了解。在Oracle 11g 以前,如果我们要添加一...
SQL> alter table test6u add constraint uni_test7 unique (object_id); Table altered. ---在表中dba_constraint查询约束内容 select constraint_name,table_name,constraint_type from dba_constraints where owner='AIKI2' and table_name in ('TEST6','TEST6U') ...
In the new row, complete the following fields: Name: The name of the constraint. ID: The unique ID of the constraint. Type: The type of the constraint. Responsible Company: The company responsible for addressing the constraint. By default, a new constraint is assigned to the current user'...