语法:`ADD CONSTRAINT FK_ForeignKeyName FOREIGN KEY (ForeignKeyColumn) REFERENCES ReferenceTable (ReferenceColumn)` 检查约束 (Check) 检查约束用于限制列中的值范围或条件。 语法:`ADD CONSTRAINT CK_ConstraintName CHECK (Condition)` 默认值约束 (Default) 默认值约束为列提供默认值,当插入新行时,如果没有指定...
alter table 表名 add constraint 约束名 primary key (主键) --添加唯一约束 alter table 表名 add constraint 约束名 unique (字段) ---添加默认约束 alter table 表名 add constraint 约束名 default ('默认内容') for 字段 --添加检查check约束,要求字段只能在1到100之间 alter table 表名 add constraint...
you must use a table constraint instead of acolumn constraint. Setting a single column as the primary key within the column definition is called acolumn constraint. Defining the primary key (single or composite) outside of the column definition ...
In SQL Server, all table constraints are database objects, just like tables, views, stored procedures, functions, and so on. Therefore, constraints must have unique names across the database. But because every table constraint is scoped to an individual table, it makes sense to adopt a naming...
1:--创建新表2:use MyDemo3:CREATETABLE[dbo].[Employees](4:[empid][int]IDENTITY(1,1)NOTNULL,5:[empname][nvarchar](100)NULL,6:[deptid][int]NULL,7:[Salary][float]NULL,8:CONSTRAINT[PK_Employees]PRIMARYKEYCLUSTERED9:([empid]ASC)10:WITH11:(PAD_INDEX=OFF,STATISTICS_NORECOMPUTE=OFF,IGNORE...
CONSTRAINT_SCHEMA nvarchar(128) Nama skema yang berisi batasan. Penting: Satu-satunya cara yang dapat diandalkan untuk menemukan skema objek adalah dengan mengkueri sys.objects tampilan katalog. CONSTRAINT_NAME nama sysname Nama batasan. TABLE_CATALOG nvarchar(128) Kualifikasi tabel. ...
CONSTRAINT_CATALOG nvarchar(128) Kualifikasi batasan. CONSTRAINT_SCHEMA nvarchar(128) Nama skema yang berisi batasan. Penting: Jangan gunakan tampilan INFORMATION_SCHEMA untuk menentukan skema objek. INFORMATION_SCHEMA tampilan hanya mewakili subset metadata objek. Satu-satunya cara...
(primary key constraint):要求主键列数据唯一,并且不允许为空 唯一约束(unique constraint):要求该列唯一,允许为空,但只能出现一个空值 检查约束(check constraint):某列取值范围、格式限制等,如有关年龄的约束 默认约束(default constraint):某列的默认值 外键约束(foregin key constraint):用于两表间建立关系,...
Remove the constraint from the table definition if the foreign key references a unique constraint.In SQL Server 2014 (12.x), FOREIGN KEY constraints are not supported with memory-optimized tables. Feature clustered index Specify a nonclustered index. In the case of a primary key index be sure...
CONSTRAINT PK_MemorySchemaAndData PRIMARY KEY NONCLUSTERED HASH (id) WITH (BUCKET_COUNT = 150000) ) WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA) CREATE TABLE MemorySchemaOnly ( id int NOT NULL, c1 nchar(1) NOT NULL, ...