Working With Nested Table Oracle

Nested table is awesome feature of Oracle. You can create table inside a table, Which means one column can be treated as a table.
Nested tables are faster than the parent child table relationship.

Steps :

• Create Object TYPE

CREATE OR REPLACE TYPE emp_rec_type AS OBJECT
   (
     EMPNO NUMBER (4),
     ENAME VARCHAR2 (10 BYTE),
     JOB VARCHAR2 (9 BYTE),
     MGR NUMBER (4),
     HIREDATE DATE,
     SAL NUMBER (7, 2),
     COMM NUMBER (7, 2)
     );

•  Create Table type

CREATE TYPE emp_table_type AS TABLE OF emp_rec_type;

• Create Table with Object type

CREATE TABLE dept_details(   DEPTNO      NUMBER (2),   DNAME       VARCHAR2 (14 BYTE),   LOC         VARCHAR2 (13 BYTE),   employees   emp_table_type)NESTED TABLE employees   STORE AS emp_tab_index;

• emp_tab_index is nested table index

• Need to create table  and insert data in dept and emp tables (If not exist in db )

CREATE TABLE DEPT
(
   DEPTNO   NUMBER (2) CONSTRAINT PK_DEPT PRIMARY KEY,
   DNAME    VARCHAR2 (14),
   LOC      VARCHAR2 (13)
);
/
CREATE TABLE EMP
(
   EMPNO      NUMBER (4) CONSTRAINT PK_EMP PRIMARY KEY,
   ENAME      VARCHAR2 (10),
   JOB        VARCHAR2 (9),
   MGR        NUMBER (4),
   HIREDATE   DATE,
   SAL        NUMBER (7, 2),
   COMM       NUMBER (7, 2),
   DEPTNO     NUMBER (2) CONSTRAINT FK_DEPTNO REFERENCES DEPT
);
/
INSERT INTO DEPT VALUES (10,'ACCOUNTING','NEW YORK');
INSERT INTO DEPT VALUES (20,'RESEARCH','DALLAS');
INSERT INTO DEPT VALUES (30,'SALES','CHICAGO');
INSERT INTO DEPT VALUES (40,'OPERATIONS','BOSTON');
INSERT INTO EMP VALUES (7369,'SMITH','CLERK',7902,to_date('17-12-1980','dd-mm-yyyy'),800,NULL,20);
INSERT INTO EMP VALUES (7499,'ALLEN','SALESMAN',7698,to_date('20-2-1981','dd-mm-yyyy'),1600,300,30);
INSERT INTO EMP VALUES (7521,'WARD','SALESMAN',7698,to_date('22-2-1981','dd-mm-yyyy'),1250,500,30);
INSERT INTO EMP VALUES (7566,'JONES','MANAGER',7839,to_date('2-4-1981','dd-mm-yyyy'),2975,NULL,20);
INSERT INTO EMP VALUES (7654,'MARTIN','SALESMAN',7698,to_date('28-9-1981','dd-mm-yyyy'),1250,1400,30);
INSERT INTO EMP VALUES (7698,'BLAKE','MANAGER',7839,to_date('1-5-1981','dd-mm-yyyy'),2850,NULL,30);
INSERT INTO EMP VALUES (7782,'CLARK','MANAGER',7839,to_date('9-6-1981','dd-mm-yyyy'),2450,NULL,10);
INSERT INTO EMP VALUES (7788,'SCOTT','ANALYST',7566,to_date('13-JUL-87','dd-mm-rr')-85,3000,NULL,20);
INSERT INTO EMP VALUES (7839,'KING','PRESIDENT',NULL,to_date('17-11-1981','dd-mm-yyyy'),5000,NULL,10);
INSERT INTO EMP VALUES (7844,'TURNER','SALESMAN',7698,to_date('8-9-1981','dd-mm-yyyy'),1500,0,30);
INSERT INTO EMP VALUES (7876,'ADAMS','CLERK',7788,to_date('13-JUL-87', 'dd-mm-rr')-51,1100,NULL,20);
INSERT INTO EMP VALUES (7900,'JAMES','CLERK',7698,to_date('3-12-1981','dd-mm-yyyy'),950,NULL,30);
INSERT INTO EMP VALUES (7902,'FORD','ANALYST',7566,to_date('3-12-1981','dd-mm-yyyy'),3000,NULL,20);
INSERT INTO EMP VALUES (7934,'MILLER','CLERK',7782,to_date('23-1-1982','dd-mm-yyyy'),1300,NULL,10);
/
COMMIT;

• INSERT into Nested table

DECLARE
   CURSOR c_dept
   IS
      SELECT deptno, dname, loc FROM dept;
   TYPE l_dept_rec_type IS RECORD
   (
      DEPTNO   dept.deptno%TYPE,
      DNAME    dept.DNAME%TYPE,
      LOC      dept.LOC%TYPE
   );
   TYPE l_dept_tab_type IS TABLE OF l_dept_rec_type;
   l_dept_no        l_dept_tab_type;
   CURSOR c_emp_list (P_DEPTNO DEPT.DEPTNO%TYPE)
   IS
      SELECT emp_rec_type (EMPNO,
                           ENAME,
                           JOB,
                           MGR,
                           HIREDATE,
                           SAL,
                           COMM)
        FROM EMP
       WHERE deptno = P_DEPTNO;
   l_EMP_list_tab   emp_table_type;
BEGIN
   OPEN c_dept;

   FETCH c_dept
   BULK COLLECT INTO l_dept_no;
   CLOSE c_dept;
   FOR i IN l_dept_no.FIRST .. l_dept_no.LAST
   LOOP
      OPEN c_emp_list (l_dept_no (i).deptno);
      FETCH c_emp_list
      BULK COLLECT INTO l_EMP_list_tab;
      CLOSE c_emp_list;
      INSERT INTO dept_details (DEPTNO,
                                DNAME,
                                LOC,
                                employees)
           VALUES (l_dept_no (i).deptno,
                   l_dept_no (i).dname,
                   l_dept_no (i).loc,
                   l_EMP_list_tab);
   END LOOP;
commit;
END;

• Select Data from nested table

SELECT ee.empno,
                ee.ename,
                ee.comm
  FROM dept_details dd,
            TABLE (employees) ee
 WHERE ee.empno = 7788;

• UPDATE data in Nested Table

  UPDATE TABLE (SELECT dept_details.employees
                FROM dept_details
               WHERE dept_details.deptno = 10)
   SET comm = 9000
 WHERE empno = 7839;

• Delete from Nested table

 DELETE TABLE (SELECT dept_details.employees
                FROM dept_details
               WHERE dept_details.deptno = 10)
 WHERE empno = 7839;