[SQL Server] Create a table-auto-increment field and primary key

Create Table ds_tcategory -- problem category information table (categoryidint identity () primary key, -- category ID, primary key, automatically increasing categorynamevarchar (20) uniquenot null, -- category name (such as default, Major, c ++, C, C #, Java, JavaScript, Web (HTML, CSS, XML), JS) qcountint default 0, -- number of problems under this category showint default 1, -- whether to display this class in the problem list (1-Display (default), 0-not display) descriptionvarchar (500) -- description of this class, description)