2.主键约束 --Primary keyALTERTABLEdbo.EmployeesADDCONSTRAINTPK_EmployeesPRIMARYKEY(empid); 对于主键约束后台将创建一个唯一索引,以物理机制强制逻辑的唯一性约束 3.唯一约束 --UniqueALTERTABLEdbo.EmployeesADDCONSTRAINTUNQ_Employees_ssnUNIQUE(ssn);
PK_CreateConstraint2_id primary key(id) --添加唯一约束 alter table T_CreateConstraint2 add constraint UQ_CreateConstraint2_name unique(name) --添加默认约束 alter table T_CreateConstraint2 add constraint DF_CreateConstraint2_joinDate default (getdate()) for jionDate --添加外键约束 alter table F...
主键约束 (Primary Key) 主键是表中的唯一标识符,用于确保每行数据的唯一性。 语法:`ADD CONSTRAINT PK_ColumnName PRIMARY KEY (ColumnName)` 外键约束 (Foreign Key) 外键用于建立两个表之间的关系,确保引用数据的完整性。 语法:`ADD CONSTRAINT FK_ForeignKeyName FOREIGN KEY (ForeignKeyColumn) REFERENCES Refer...
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_...
主键约束(Primary Key Constraints) 每个表只能定义一个主键。 添加主键约束: --为表添加主键约束Primary Key Constraints ALTER TABLE dbo.Employees ADD CONSTRAINT PK_Employees PRIMARY KEY(empid); 1. 2. 3. 4. 唯一约束(Unique Constraints) ...
CONSTRAINT PK_TransactionHistoryArchive primary key NONCLUSTERED HASH WITH (BUCKET_COUNT = 100000), [ProductID] [int] NOT NULL, [ReferenceOrderID] [int] NOT NULL, [ReferenceOrderLineID] [int] NOT NULL, [TransactionDate] [datetime] NOT NULL, ...
1:ALTERTABLEdbo.EmployeesADDSalary_Tax1 float,update_flag bit2:ALTERTABLEdbo.EmployeesADDCONSTRAINTDF_Employees_update_flagDEFAULT0FORupdate_flag3:Schedule the belowDMLupdate by an appropriate frequency according to your workload4:Update EmployeessetSalary_Tax1=Salary-100WHEREUPDATE_Flag=05:Then you ...
add constraint PK_stuNo primary key(stuNo); -- 唯一约束:UQ_字段名 alter table stuInfo add constraint UQ_stuNo unique(stuID); -- 默认值约束:DF_字段名 alter table stuInfo add constraint DF_stuBirthday default('2000-2-2') for stuBirthday; ...
(100) UNIQUE ); ``` - **添加唯一约束**: ```sql ALTER TABLE Users ADD CONSTRAINT UC_Email UNIQUE (Email); ``` 或者,在创建表时直接指定唯一约束: ```sql CREATE TABLE Users ( UserID INT PRIMARY KEY, UserName VARCHAR(50) NOT NULL, PhoneNumber VARCHAR(20), CONSTRAINT UC_PhoneNumber ...
MERGE statement throws Violation of PRIMARY KEY constraint ''. Cannot insert duplicate key in object '' exception in SQL Server 2008 merge the output of two stored procedures Microsoft SQL Server Error 5170 when creating table Migrate an execution plan from one sql server instance to another Migra...