SQL PRIMARY key auto-numbering primary key self-increment

1. Create a new data table with the field ID, set the ID as the primary key

The code is as follows: CREATE TABLE TB (ID int,constraint pkid primary key (ID)) CREATE TABLE TB (ID int primary key)

2. Create a new data table with field ID, set ID as primary key and auto number

The code is as follows: CREATE TABLE TB (ID int identity (constraint), Pkid primary key (ID)), CREATE table TB (ID int identity) Primary K EY)

3. A data table has been built, with field IDs, set the ID as the primary key

The code is as follows: ALTER TABLE TB ALTER COLUMN ID int NOT NULL
ALTER TABLE TB ADD constraint Pkid primary key (ID)

4. Delete primary key

The code is as follows: Declare @Pk VarChar (100); Select @Pk =name from sysobjects where parent_obj=object_id (' TB ') and xtype= ' Pk '; If @Pk is not null exec (' Alter table TB Drop ' + @Pk)