ALTER TABLE [表名] DROP COLUMN [字段名] 修改字段: ALTER TABLE [表名] ALTER COLUMN [字段名] NVARCHAR (50) NULL 重命名表:(Access 重命名表,请参考文章:在Access数据库中重命名表) sp_rename \'表名\', \'新表名\', \'OBJECT\' 新建约束: ALTER TABLE [表名]
SQL> SELECT * FROM user_cons_columns WHERE table_name = 'TB_CONSTRAINT_3'; OWNER CONSTRAINT_NAME TABLE_NAME COLUMN_NAME POSITION --- --- --- --- --- ROBINSON SYS_C005554 TB_CONSTRAINT_3 EMAIL 1 ROBINSON PK_TB_CONS3_EMPNO_ENAME TB_CONSTRAINT_3 ENAME 2 ROBINSON PK_TB_CONS3_EMPNO...
Drop Column 列名 Cascade/Restrict Alter Column 列名 数据类型 Modify Column 列名 数据类型(modify用于修改列属性) *约束: Add 表级约束 Add Constraint 约束名 约束条件 Drop Constraint 约束名 Cascade/Restrict【默认】 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. ...
You can add multiple columns in a single ALTER TABLE command as well. You’ll just need to surround the column details in brackets, and separate them with commas. This is slightly different from other databases which don’t require the brackets. ALTERTABLEcustomerADD(suburb VARCHAR2(100),postc...
字段定义constraint 约束名约否类型(字段名)-->unique,primary key,check 字段定义constraint 约否名foreingn key (字段名)references 表名(字段名)--->foreign 三、建表时约束定义 1.定义各种不同的约束 --创建一个用于作外键的表tb_dept SQL> CREATE TABLE tb_dept ...
{ ADD COLUMN <列名> <类型>-- 增加列ALTER TABLE 职员 ADD 年末奖金 Money NULL(为职员表添加列,列名为年末奖金,允许为空值,数据类型为货币数据类型。) | CHANGE [COLUMN] <旧列名> <新列名> <新列类型>-- 修改列名或类型 | ALTER [COLUMN] <列名> { SET DEFAULT <默认值> | DROP DEFAULT }-- ...
--SQL基础--> 约束(CONSTRAINT) --=== 一、几类数据完整性 实体完整性:表中记录不反复(不论什么两条记录不全等)而且每条记录都有一个非空主键 域完整性:表中字段值必须与字段数据类型、格式、有效范围相吻合 參照完整性:不能引用不存在的值 自己定义...
[ CONSTRAINT constraint_name ] { [ NULL | NOT NULL ] { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] [ WITH FILLFACTOR =fillfactor ] [ WITH ( index_option [, ...n ] ) ] [ ON { partition_scheme_name (partition_column_name) | filegroup | "default" } ] | [ FOREIGN KEY...
其中表约束table_constraint为: [ CONSTRAINT constraint_name ] { CHECK ( expression ) | UNIQUE ( column_name [, ... ] ) index_parameters | PRIMARYKEY( column_name [, ... ] )index_parameters | PARTIAL CLUSTERKEY( column_name [, ... ] )} [ DEFERRABLE | NOT DEFERRABLE | INITIALLY DEF...
ALTER TABLE fails and an error is returned. When a new PRIMARY KEY or UNIQUE constraint is added to an existing column, the data in the column or columns must be unique. If duplicate values are found, ALTER TABLE fails. TheWITH NOCHECKoption has no effect when PRIMARY KEY or UNIQUE cons...