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....
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. Note For ...
CREATE UNIQUE INDEX UQ_Email语句用于创建一个唯一索引,名为UQ_Email。 ON Employees (Email)指定了索引是在Employees表的Email字段上创建的。 如果想使用唯一约束来实现一样的目的,也可以如下操作: ALTERTABLEEmployeesADDCONSTRAINTUQ_EmailUNIQUE(Email); 1. 2. ALTER TABLE Employees用于修改已有的表结构。 ADD C...
SQL UNIQUE Constraint on CREATE TABLE 下面的 SQL 在 "Persons" 表创建时在 "Id_P" 列创建 UNIQUE 约束: MySQL: CREATE TABLE Persons ( Id_P int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255),UNIQUE (Id_P)) SQL Server / Oracle...
To create a unique constraint, using: SQL Server Management Studio Transact-SQL Before You Begin Security Permissions Requires ALTER permission on the table. [Top] Using SQL Server Management Studio To create a unique constraint In Object Explorer, right-click the table to which you want to add...
For more information, see Unique Constraints and Check Constraints and Primary and Foreign Key Constraints. Index independent of a constraint Multiple unique nonclustered indexes can be defined on a table. For more information, see CREATE INDEX (Transact-SQL). Indexed view To create an indexed view...
IUniqueConstraint CreateUniqueConstraint(Microsoft.SqlServer.Management.SqlParser.Metadata.ITabular parent, Microsoft.SqlServer.Management.SqlParser.Metadata.IRelationalIndex index); Parameters parent ITabular index IRelationalIndex Returns IUniqueConstraint Applies to 產品版本 Micros...
2)SQL约束(6 个) (1)NOT NULL(一种写法) createtablecourse( cidintnotnull,cnamevarchar(255), tidint); (2)UNIQUE(三种写法) createtablecourse( cidintnotnull, cnamevarchar(255)notnullunique,tidint,unique(cid),CONSTRAINTuc_courseIDunique(cid, tid)--命名多列约束); ...
add constraint pk_employeeid primary key (id) 4:外键约束 外键约束用在确保数据完整性和两个表之间的关系上 先看例子 create table orders ( id int identity not null primary key, customerid int not null foreign key references customer(id), ...
UNIQUE constraints 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 Constr...