برجاء شرح ما هو ال Index Table type ، و متى يستخدم ؟

يا جماعة ...هل السؤال صعب ياجماعة !!!!؟

السلام عليكم
انا ايضا اريد معرفة الرد ؟؟؟

There are many type of the composite data types:
1 - pl/sql records to deal with the table records
2 - index by table to deal with the table columns

** that if you want to get an individual value from a table like the employee name for the employee no =7902 then you can put it in a scalar variable like :

DECALRE
V_ENAME EMP.ENAME%TYPE;
BEGIN SELECT ENAME INTO V_ENAME FROM EMP WHERE EMPNO=7902;
  DBMS_OUTPUT.PUT_LINE(V_ENAME);
END;

** BUT IF YOU WANT TO GET THE ALL INFORMATION FOR THAT EMPLOYEE , YOU CAN DECALRE A VARIABLE FOR EVERY COLUMN OR DECLARE ONE VARAIBLE AS RECORD TO PUT ALL INFORMATION IN IT LIKE :

DECALRE
V_EMP_REC EMP%ROWTYPE;
BEGIN SELECT * INTO V_EMP_REC FROM EMP WHERE EMPNO=7902;
  DBMS_OUTPUT.PUT_LINE(V_EMP_REC.V_ENAME ||' , ' ||V_EMP_REC.SAL);
END;

** BUT IF YOU WANT TO GET THE ALL EMPLOYEES NAMES THEN YOU CAN DECALRE A VARIABLE WITH INDEX BY TABLE LIKE:

DECALRE
TYPE EMP_TABLE_TYPE IS TABLE OF EMPLOYEES.FIRST_NAME%TYPE INDEX BY PLS_INTEGER;
EMP_TABLE  EMP_TABLE_TYPE;
Z  NUMBER:=0;
BEGIN FOR i IN 1..10 LOOP
     Z:=100+i ;
     SELECT FIRST_NAME  INTO EMP_TABLE(I) FROM EMPLOYEES 
        WHERE EMPLOYEE_ID=Z ;
        DBMS_OUTPUT.PUT_LINE(EMP_TABLE.FIRST_NAME);
END;

شكرا يا استاذ نادر على الشرح