alter table 外键表名 add constraint 约束名称 foreign key(外键字段) references 主键表名(约束列名) 1. 3、Unique约束 唯一约束确保表中的一列数据没有相同的值。与主键约束类似,唯一约束也强制唯一性,但唯一约束用于非主键的一列或者多列的组合,且一个表可以定义多个唯一约束。 create unique index u_index o...
createtime datetime default(getdate()) ); go create table student( id int primary key, sno varchar(50) not null unique, name varchar(50) not null check(len(name)<5), score float not null default(-1), classid int ); go ALTER TABLE student ADD CONSTRAINT FK_student_class FOREIGN KEY...
FILESTREAM_ON { partition_scheme_name | filegroup | "default" } 適用於:SQL Server 2008 R2 (10.50.x) 和更新版本。 Azure SQL Database 和 Azure SQL 受控執行個體不支援 FILESTREAM。 為FILESTREAM 資料指定檔案群組。 如果此資料表包含 FILESTREAM 資料,而且資料表已分割,則必須包含 FILESTREAM_ON 子句,而...
Use a named constraint When working with database projects, it's recommended to create constraints with names. Otherwise, the default constraint is given a system-generated name, which will differ on each SQL server environment where your database objects are created. SQLKopija CREATETABLEdbo.doc_...
ON { partition_scheme | filegroup | "default" } can also be specified in a PRIMARY KEY or UNIQUE constraint. These constraints create indexes. If filegroup is specified, the index is stored in the named filegroup. If "default" is specified, or if ON isn't specified at all, the index ...
{ filegroup | "default" } ] ] | [ CHECK ( logical_expression ) ] [ , ...n ] } <computed_column_definition> ::= column_name AS computed_column_expression ::= { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ , ...n ] [ WITH FILL...
CREATETABLEMyTable ( mycolumnnn1nvarchar, mycolumn2nvarcharCOLLATEFrisian_100_CS_AS )WITH( CLUSTERED COLUMNSTOREINDEX) ; B. Specify a DEFAULT constraint for a column The following example shows the syntax to specify a default value for a column. ThecolAcolumn has a default constraint namedconstr...
SQL 语法总结 完整性约束 NOT NULL 列值非空 DEFAULT 列的默认值 UNIQUE 限制列取值不能重复 CHECK 限制列的取值范围 PRIMARY KEY 主键 FOREIGN KEY 外码 定...
step2,分别在两台Server上创建数据库和表,数据库分别是DBtest1 和 DBTest2,将DBTest1作为Master DB,将DBTest2作为Slave DB。 --default instanceCREATETABLE[dbo].[Person]([PersonID][int]NOTNULL,[PersonType][nchar](2)NOTNULL,[FirstName]sysname,[MiddleName]sysname ,[LastName]sysname,constraintchk__Pers...
There is already an object named 'PK_Product_ProductID' in the database. Msg 1750, Level 16, State 0, Line 11 Could not create constraint or index. See previous errors. 如上所示,约束也是唯一的,它跟表名一样。而且也是跟Schema有关系,如下所示,下面SQL是OK的。