The SQL statement (eight) that must be the integrity constraint of the database

Entity integrity

 1. Defining a primary key when building a tableCreate Table Table name   (Sno int identity (+),Sname nvarchar (),--Set Primary keyPrimary Key (Sno)   )2. Add a primary keyALTER TABLE table nameadd constraint pk_ table name _snoprimary KEY (ID) Referential Integrity1. Define a foreign key when building a tableCREATE TABLE table name  (Sno int Identity (primary) key,CNO int not NULL,foreign Key (CNO) ReferencesTable Name 2 (Cno)On Delete cascade --Cascade Delete On update Cascade --Cascade update --On delete control on action Delete  )2. Add a foreign keyALTER TABLE table nameadd constraint Fk_ table name _ Table Name 2Foreign Key (CID) references table Name 2 (CID)  user-defined integrity1. Non-null constraintsALTER TABLE table nameALTER COLUMN name varchar (NOT NULL)2. Unique ConstraintsALTER TABLE table nameadd constraint uq_ table name _ Column name unique (column)3. Check ConstraintsALTER TABLE table nameadd constraint Ck_ table name _ Column name Check (age>5)4. Default ConstraintsALTER TABLE table nameadd constraint df_ table name _ Column name default (' Male ')For gender Delete Constraint--delete constraintALTER TABLE name drop constraint df_ table name _ column

The SQL statement (eight) that must be the integrity constraint of the database