Tutorial on trigger and integretiy constraints

5 Integrity Constraints and Triggers5.1 IntegritytsIn Section 1 we have discussed three types of integrity constraints: not null constraints, primarykeys, and unique constraints. In this section we introduce two more types of constraints thatcan be specified within the create table statement: check constraints (to restrict possibleattribute values), and foreign key constraints (to specify interdependencies between relations).5.1.1 Check ConstraintsOften columns in a table must have values that are within a certain range or that satisfy certainconditions. Check constraints allow users to restrict possible attribute values for a column toadmissible ones. They can be specified as column constraints or table constraints. The syntaxfor a check constraint is[constraint ] check()If a check constraint is specified as a column constraint, the condition can only refer thatcolumn.Example: The name of an employee must consist of upper case letters only; the minimumsalary of an employee is 500; department numbers must range between 10 and100:create table EMP(...,ENAME varchar2(30) constraint check namecheck(ENAME = upper(ENAME)),SAL number(5,2) constraint check sal check(SAL >= 500),DEPTNO number(3)t check deptnocheck(DEPTNO between 10 and 100) );If a check constraint is specified as a table constraint, can refer to all columnsof the table. Note that only simple conditions are allowed. For example, it is not allowedto refer to ...