alter table employee_info modify sex char(2); //3.4 修改默认值 alter table employee_info modify hiredate default sysdate+1; //4.禁用约束 alter table employee_info disable constraint uq_emp_info; //5.启用约束 alter table employee_info enable constraint uq_emp_info; //6.延迟约束...
ALTER TABLE Student add constraint uqe_phone unique (phone); --删除约束 ALTER TABLE Student drop constraint uqe_phone; --约束失效 ALTER TABLE Student disable constraint uqe_phone; --约束复效 ALTER TABLE Student enable constraint uqe_phone; --修改表名 ALTER TABLE Student RENAME TO Student2 -...
alter table dirk_emp drop column score; -- contraint disable or enable 禁用约束 启用约束 alter table dirk_emp disable constraint dirk_emp_num_uk; alter table dirk_emp enable constraint dirk_emp_num_uk; 1. 2. 3. 4. 5. 6. 7.
To enable a UNIQUE or PRIMARY KEY constraint, you must have the privileges necessary to create an index on the table. You need these privileges because Oracle creates an index on the columns of the unique or primary key in the schema containing the table. To enable or disable triggers, ...
ALTER TABLE...DISABLE KEYS让MySQL停止更新MyISAM表中的非唯一索引。然后使用ALTER TABLE ... ENABLE KEYS重新创建丢失的索引。进行此操作时,MySQL采用一种特殊的算法,比一个接一个地插入关键字要快很多。因此,在进行成批插入操作前先使关键字禁用可以大大地加快速度。使用ALTER TABLE ... DISABLE KEYS除了需要...
{ENABLE | DISABLE} CONSTRAINT constraint_name 修改约束的状态,支持外键约束或 CHECK 约束。 示例 修改表 tbl1 中字段 col1 的字段长度。 obclient> CREATE TABLE tbl1(col1 VARCHAR2(5)); Query OK, 0 rows affected obclient> ALTER TABLE tbl1 MODIFY col1 VARCHAR2(10); Query OK, 0 rows affected...
ALTER TABLE ACCOUNTS DROP CONTRAINT yy; 3、向表中添加主键约束 ALTER TABLE ACCOUNTS ADD CONSTRAINT PK_ACCOUNTS PRIMARY KEY(ACCOUNTS_NUMBER); oracle中not null约束是我们用到的最多的约束之一了。我们可以在创建表时让系统自动指定not null约束的名字来创建,也可以手动的的指定not null约束的名字来创建,也可以...
After migrating from Oracle 10.2 to Oracle 11.2, a problem occurs when attempting to re-enable foreign keys on a table that was loaded. On a fact table we disable the constraints, then load the table, then enable the constraints with the NOVALIDATE option. Now it gets an ORA-00054 because...
ALTER TABLE s_emp DISABLE CONSTRAINT s_emp_id_pk CASCADE; 2、可以通过ENABLE关键点来开启约束,使得约束有效 ALTER TABLE s_emp ENABLE CONSTRAINT s_emp_id_pk 六、DROP TABLE 语法 删除一个表 DROP TABLE table [CASCADE constraints]; l 将表和数据一起删除 ...