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...
CREATE TABLE dbo.T1 ( column_1 AS 'Computed column ' + column_2, column_2 varchar(30) CONSTRAINT default_name DEFAULT ('my column default'), column_3 rowversion, column_4 varchar(40) NULL ); GO INSERT INTO dbo.T1 (column_4) VALUES ('Explicit value'); INSERT INTO dbo.T1 (column...
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...
CREATE TABLE dbo.T1 ( column_1 AS 'Computed column ' + column_2, column_2 varchar(30) CONSTRAINT default_name DEFAULT ('my column default'), column_3 rowversion, column_4 varchar(40) NULL ); GO INSERT INTO dbo.T1 (column_4) VALUES ('Explicit value'); INSERT INTO dbo.T1 (column...
适用于:SQL Server Azure SQL 数据库 Azure SQL 托管实例 Microsoft Fabric SQL 数据库在数据库中创建新表。备注 有关Microsoft Fabric 中仓库的引用,请访问 CREATE TABLE (Fabric 数据仓库)。 有关Azure Synapse Analytics 和 Analytics Platform System (PDW) 的参考,请访问 CREATE TABLE (Azure Synapse Analytics...
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. ...
When you create a UNIQUE constraint, a unique nonclustered index is created to enforce a UNIQUE constraint by default. You can specify a unique clustered index if a clustered index on the table does not already exist. For more information, seeUnique Constraints and Check ConstraintsandPrimary and...
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。
CREATETABLEdbo.doc_exz ( column_aINT, column_bINTDEFAULT50); Use a named constraint SQL CREATETABLEdbo.doc_exz ( column_aINT, column_bINTCONSTRAINTDF_Doc_Exz_Column_BDEFAULT50); Related content Povratne informacije Je li ova stranica bila od pomoći?
Applies to: SQL Server 2014 (12.x) and later versions, and Azure SQL DatabaseWhen ON, the statistics created are per partition statistics. When OFF, the statistics tree is dropped and SQL Server recomputes the statistics. The default is OFF....