[sql] How To Create Table with Identity Column

I have an existing table that I am about to blow away because I did not create it with the ID column set to be the table's Identity column.

Using SQL Server Management Studio, I scripted a "Create To..." of the existing table and got this:

CREATE TABLE [dbo].[History](
    [ID] [int] NOT NULL,
    [RequestID] [int] NOT NULL,
    [EmployeeID] [varchar](50) NOT NULL,
    [DateStamp] [datetime] NOT NULL,
 CONSTRAINT [PK_History] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

My question is, how would I modify this SQL so that my resulting table has the ID column set as the Identity?

This question is related to sql sql-server tsql

The answer is


CREATE TABLE [dbo].[History](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [RequestID] [int] NOT NULL,
    [EmployeeID] [varchar](50) NOT NULL,
    [DateStamp] [datetime] NOT NULL,
 CONSTRAINT [PK_History] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON)
) ON [PRIMARY]

This has already been answered, but I think the simplest syntax is:

CREATE TABLE History (
    ID int primary key IDENTITY(1,1) NOT NULL,
    . . .

The more complicated constraint index is useful when you actually want to change the options.

By the way, I prefer to name such a column HistoryId, so it matches the names of the columns in foreign key relationships.


[id] [int] IDENTITY(1,1) NOT NULL,

of course since you're creating the table in SQL Server Management Studio you could use the table designer to set the Identity Specification.

enter image description here


Unique key allows max 2 NULL values. Explaination:

create table teppp
(
id int identity(1,1) primary key,
name varchar(10 )unique,
addresss varchar(10)
)

insert into teppp ( name,addresss) values ('','address1')
insert into teppp ( name,addresss) values ('NULL','address2')
insert into teppp ( addresss) values ('address3')

select * from teppp
null string , address1
NULL,address2
NULL,address3

If you try inserting same values as below:

insert into teppp ( name,addresss) values ('','address4')
insert into teppp ( name,addresss) values ('NULL','address5')
insert into teppp ( addresss) values ('address6')

Every time you will get error like:

Violation of UNIQUE KEY constraint 'UQ__teppp__72E12F1B2E1BDC42'. Cannot insert duplicate key in object 'dbo.teppp'.
The statement has been terminated.


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