Define a primary key in the SQL Server Database Engine by using SQL Server Management Studio or Transact-SQL.
2.2)外键(约束)创建(不推荐使用,一般不进行外键约束,只进行外键约定): alert table 主键表名 add constraint FK_ID(外键名称) foreign key(外键字段名) references 外表表名(主键字段名) 2.3)外键出现的情况: 补充: 在创建表的时候,表和表之间可能会存在的业务关系(关联关系),这时会产生外键。 关联关系中存在...
altertablePersonsaddunique(id_p);altertablePersonsadd constraintuc_PersonIDunique(id_p, lastname); 2)PRIMARY KEY(两种写法) --注:如果使用ALTER TABLE语句添加主键,必须把主键列声明为不包含NULL值(在表首次创建时)。 altertablePersonsaddprimarykey(id_p);altertablePersonsadd constraintuc_PersonIDprimaryke...
程序集:Microsoft.SqlServer.Management.SqlParser(在 Microsoft.SqlServer.Management.SqlParser.dll 中) 语法 C# IPrimaryKeyConstraintCreatePrimaryKeyConstraint(ITabular parent, IRelationalIndex index) 参数 parent 类型:Microsoft.SqlServer.Management.SqlParser.Metadata.ITabular ...
You can create a unique constraint in SQL Server by using SQL Server Management Studio or Transact-SQL to ensure no duplicate values are entered in specific columns that don't participate in a primary key. Creating a unique constraint automatically creates a corresponding unique index....
SQL 复制 --Create the tables and insert the values. CREATE TABLE dbo.SUPPLY1 ( supplyID INT PRIMARY KEY CHECK (supplyID BETWEEN 1 and 150), supplier CHAR(50) ); CREATE TABLE dbo.SUPPLY2 ( supplyID INT PRIMARY KEY CHECK (supplyID BETWEEN 151 and 300), supplier CHAR(50) ); ...
id int identity not null primary key, customerid int not null foreign key references customer(id), orderdate smalldatetime not null, eid int not null ) 注意:这个表的外键必须是另一个表的主键! 在现有表上添加外键 alter table orders add constraint fk_employee_creator_order ...
A clustered index is built on a table variable when a primary key constraint is added. Similarly, a nonclustered index is built on a table variable when a unique constraint is added. When the table variable goes out of scope, the indexes are dropped....
But you cannot include additional columns in a Primary Key constraint. You can implement the identical physical design by adding a unique, non-clustered index with included columns. Also there's nothing wrong with using a UNIQUEIDENTIFIER for the clustered index key, so long as your...
SQL 複製 --Create the tables and insert the values. CREATE TABLE dbo.SUPPLY1 ( supplyID INT PRIMARY KEY CHECK (supplyID BETWEEN 1 and 150), supplier CHAR(50) ); CREATE TABLE dbo.SUPPLY2 ( supplyID INT PRIMARY KEY CHECK (supplyID BETWEEN 151 and 300), supplier CHAR(50) ); ...