PRIMARY KEY

Essentially the same as a clustered index that is unique.

The primary key defines the order by which the records are stored in (most of the time, the DB might choose a different index), and all instances must be unique.

CREATE TABLE SchameName.TableName(
	ColName1 smallint IDENTITY(1,1) NOT NULL PRIMARY KEY,
	ColName2 VARCHAR(50) UNIQUE,
)

CREATE TABLE SchameName.TableName(
	ColName1 smallint IDENTITY(1,1) NOT NULL,
	ColName2 VARCHAR(50) UNIQUE,
	CONSTRAINT pk_ColName1 PRIMARY KEY (ColName1)
)