Constraint Constraint Type Meaning
CHECKCSpecifies a certain condition for a column, or group of columns.
NOT NULLCNot null column
PRIMARY KEYPprimary key
FOREIGN KEYRforeign key
UNIQUEUunique
CHECK OPTIONVSpecifies that DML operations on a view must satisfy the subquery.
READ ONLYOSpecifies that a view may only be read from.
SQL> CREATE TABLE pet (
2 id NUMBER(38) CONSTRAINT pk_pet PRIMARY KEY NOT NULL
3 );
Table created.
SQL>
SQL> drop table pet;
Table dropped.
SQL>