Subquery as a column : Nested Subquery « Query Select « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. Query Select
3. Nested Subquery

SQL>
SQL>
SQL> create table departments
  2  ( deptno NUMBER(2)
  3  , dname  VARCHAR2(10)
  4  , location VARCHAR2(20)
  5  , mgr    NUMBER(4)
  6  ) ;

Table created.

SQL>
SQL> insert into departments values (10,'ACCOUNTING','NEW YORK' ,  2);

1 row created.

SQL> insert into departments values (20,'TRAINING',  'VANCOUVER',  3);

1 row created.

SQL> insert into departments values (30,'SALES',     'CHICAGO',    4);

1 row created.

SQL> insert into departments values (40,'HR',        'BOSTON',     5);

1 row created.

SQL>
SQL>
SQL> create table employees(
  2    empno      NUMBER(4)
  3  , ename      VARCHAR2(8)
  4  , init       VARCHAR2(5)
  5  , job        VARCHAR2(8)
  6  , mgr        NUMBER(4)
  7  , bdate      DATE
  8  , msal       NUMBER(6,2)
  9  , comm       NUMBER(6,2)
 10  , deptno     NUMBER(2) ) ;

Table created.

SQL>
SQL>
SQL> insert into employees values(1,'Jason',  'N',  'TRAINER', 2,   date '1965-12-18',  800 , NULL,  10);

1 row created.

SQL> insert into employees values(2,'Jerry',  'J',  'SALESREP',3,   date '1966-11-19',  1600, 300,   10);

1 row created.

SQL> insert into employees values(3,'Jord',   'T' , 'SALESREP',4,   date '1967-10-21',  1700, 500,   20);

1 row created.

SQL> insert into employees values(4,'Mary',   'J',  'MANAGER', 5,   date '1968-09-22',  1800, NULL,  20);

1 row created.

SQL> insert into employees values(5,'Joe',    'P',  'SALESREP',6,   date '1969-08-23',  1900, 1400,  30);

1 row created.

SQL> insert into employees values(6,'Black',  'R',  'MANAGER', 7,   date '1970-07-24',  2000, NULL,  30);

1 row created.

SQL> insert into employees values(7,'Red',    'A',  'MANAGER', 8,   date '1971-06-25',  2100, NULL,  40);

1 row created.

SQL> insert into employees values(8,'White',  'S',  'TRAINER', 9,   date '1972-05-26',  2200, NULL,  40);

1 row created.

SQL> insert into employees values(9,'Yellow', 'C',  'DIRECTOR',10,  date '1973-04-27',  2300, NULL,  20);

1 row created.

SQL> insert into employees values(10,'Pink',  'J',  'SALESREP',null,date '1974-03-28',  2400, 0,     30);

1 row created.

SQL>
SQL>
SQL>
SQL>
SQL> select d.deptno, d.dname, d.location
  2  ,     (select count(*)
  3         from   employees e
  4         where  e.deptno = d.deptno) as emp_count
  5  from   departments d;

DEPTNO DNAME      LOCATION             EMP_COUNT
------ ---------- -------------------- ---------
    10 ACCOUNTING NEW YORK                     2
    20 TRAINING   VANCOUVER                    3
    30 SALES      CHICAGO                      3
    40 HR         BOSTON                       2

4 rows selected.

SQL>
SQL> drop table employees;

Table dropped.

SQL>
SQL> drop table departments;

Table dropped.

SQL>
SQL>