Create a primary key in a new tableThe following example creates a table and defines a primary key on the column TransactionID in the AdventureWorks2022 database.SQL Afrita CREATE TABLE [Production].[TransactionHistoryArchive1] ( TransactionID INT IDENTITY(1, 1) NOT NULL, CONSTRAINT PK_...
The Syntax to create the Alter Table in SQL is: Alter table table_name Add constraint constraint_name Primary key (column1, column2,….column_n) Table names are the ones that add a primary key. Constraint name is the name of the primary key. The columns are the ones that make up the...
PRIMARYKEY(ID) ); SQL Server / Oracle / MS Access: CREATETABLEPersons ( ID intNOTNULLPRIMARYKEY, LastName varchar(255)NOTNULL, FirstName varchar(255), Age int ); To allow naming of aPRIMARY KEYconstraint, and for defining aPRIMARY KEYconstraint on multiple columns, use the following SQL...
23-SQL PRIMARY KEY 约束 CREATE TABLE Persons(Id_P int NOT NULL,LastName varchar(255) NOT NULL,FirstName varchar(255),Address varchar(255),City varchar(255),
Sname CHAR(20) CONSTRAINT C2 NOT NULL, Sage NUMERIC(3) CONSTRAINT C3 CHECK (Sage < 30), Ssex CHAR(2) CONSTRAINT C4 CHECK (Ssex IN ( '男','女')), CONSTRAINT StudentKey PRIMARY KEY(Sno) );在Student表上建立了5个约束条件,包括主码约束(命名为StudentKey)以及C1、C2、C3、C4四个列级约束...
Alter Stored Procedure is taking huge time in sql server Alter Table Add Column if Not Exists to update Schema Modification Script Alter Table add Column - How do you add a column after say the second column Alter table add constraint primary key clustered identity(1,1) ALTER TABLE ALTER COL...
SQL PRIMARY KEY Constraint SQL 主键约束 主键包含的都是Unique 不重复,Not NULL 不为空的数据。 The PRIMARY KEY constraint uniquely identifies each record in a table. 一个表格只能有一个主键,逐渐可以包含一个或者多个列。 SQL PRIMARY KEY on CREATE TABLE ...
Create a primary key in a new table The following example creates a table and defines a primary key on the columnTransactionIDin theAdventureWorks2022database. SQL CREATETABLE[Production].[TransactionHistoryArchive1] ( TransactionIDINTIDENTITY(1,1)NOTNULL,CONSTRAINTPK_TransactionHistoryArchive1_Transact...
PRIMARY KEY Constraints A PRIMARY KEY constraint declares one or more columns whose values uniquely identify each record in the table. It is considered a special case of the UNIQUE … - Selection from SQL in a Nutshell, 3rd Edition [Book]
If a primary key constraint is defined on more than one column, values can be duplicated within one column, but each combination of values from all the columns in the primary key constraint definition must be unique.As shown in the following illustration, the ProductID and VendorID columns in...