Oracle PL/SQL/Select Query/ROWNUM

Материал из SQL эксперт
Перейти к: навигация, поиск

Getting the Five Most Expensive Products

    
SQL>
SQL>
SQL> CREATE TABLE Product (
  2  ProductID INT NOT NULL PRIMARY KEY,
  3  Name VARCHAR(50) NOT NULL,
  4  Description VARCHAR(1000) NOT NULL,
  5  Price NUMBER NULL,
  6  ImagePath VARCHAR(50) NULL,
  7  soldout NUMBER(1,0) NULL,
  8  Promotion NUMBER(1,0) NULL);
Table created.
SQL>
SQL> CREATE SEQUENCE ProductIDSeq;
Sequence created.
SQL>
SQL> CREATE OR REPLACE TRIGGER ProductAutonumberTrigger
  2  BEFORE INSERT ON Product
  3  FOR EACH ROW
  4  BEGIN
  5     SELECT ProductIDSeq.NEXTVAL
  6     INTO :NEW.ProductID FROM DUAL;
  7  END;
  8  /
Trigger created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath,soldout, Promotion)
  2  VALUES ("Pen", "Ball Pen",5.99, "pen.jpg", 1, 0);
1 row created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath, soldout, Promotion)
  2  VALUES ("Ruler", "Long",14.99, "ruler.jpg", 0, 0);
1 row created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath, soldout, Promotion)
  2  VALUES ("Desk", "Computer Desk",5.99, "desk.jpg", 0, 1);
1 row created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath, soldout, Promotion)
  2  VALUES ("PC", "Notebook",49.99, "pc.jpg", 0, 1);
1 row created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath, soldout, Promotion)
  2  VALUES ("Mouse", "Wireless",9.99, "mouse.jpg",  1, 0);
1 row created.
SQL>
SQL> INSERT INTO Product (Name, Description, Price, ImagePath, soldout, Promotion)
  2  VALUES ("Keyboard", "keyboard",3.75, "keyboard.jpg", 0, 0);
1 row created.
SQL>
SQL> SELECT Name, Price FROM
  2       (SELECT Name, Price
  3        FROM Product
  4        ORDER BY Price DESC, Name ASC)
  5  WHERE ROWNUM<=5;
NAME                                                    PRICE
-------------------------------------------------- ----------
PC                                                      49.99
Ruler                                                   14.99
Mouse                                                    9.99
Desk                                                     5.99
Pen                                                      5.99
5 rows selected.
SQL>
SQL> drop table product;
Table dropped.
SQL> drop sequence ProductIDSeq;
Sequence dropped.



Limit the query to display only the top 3 highest paid employees.

   
SQL>
SQL>
SQL> create table employee(
  2           emp_no                 integer         primary key
  3          ,lastname               varchar2(20)    not null
  4          ,firstname              varchar2(15)    not null
  5          ,midinit                varchar2(1)
  6          ,street                 varchar2(30)
  7          ,city                   varchar2(20)
  8          ,state                  varchar2(2)
  9          ,zip                    varchar2(5)
 10          ,zip_4                  varchar2(4)
 11          ,area_code              varchar2(3)
 12          ,phone                  varchar2(8)
 13          ,salary                 number(3)
 14          ,birthdate              date
 15          ,hiredate               date
 16          ,title                  varchar2(20)
 17          ,dept_no                integer
 18          ,mgr                    integer
 19          ,region                 number
 20          ,division               number
 21          ,total_sales            number
 22  );
Table created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (1,"Anderson","Nancy","N","33 Ave","London","NY","11111","1111","212","234-1111",3.75,"21-mar-1927","1-feb-1947","Sales Manager",2,null,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (2,"Last","First","F","12 Ave","Paris","CA","22222","2222","221","867-2222",7.75,"14-feb-1976","15-mar-1985","Sales Clerk",2,1,100,10,10000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (3,"Wash","Georgia","G","1 Street14","Barton","NJ","33333","3333","214","340-3333",11.50,"2-jul-1977","21-apr-2004","Designer",1,2,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (4,"Bush","Dave","D","56 Street","Island","RI","44444","4444","215","777-4444",21.65,"15-may-1945","2-aug-1975","Designer",1,2,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (5,"Will","Robin","W","56 Street","Island","MA","55555","5555","216","777-5555",24.65,"10-dec-1980","2-aug-2007","Designer",1,5,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (6,"Pete","Mona","M","13 Ave","York","MO","66666","6666","217","111-6666",9,"14-feb-1966","15-mar-1985","Sales Clerk",2,5,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (7,"Roke","John","J","67 Ave","New York","BC","77777","7777","218","122-7777",10.00,"14-jun-1955","15-mar-1975","Accountant",3,2,100,10,40000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2               values (8,"Horry","Tedi","T","1236 Lane","Newton","NY","88888","8888","219","222-8888",13.00,"10-jun-1955","15-aug-1985","Sales Representative",3,2,100,10,50000);
1 row created.
SQL> insert into employee(emp_no, lastname, firstname, midinit, street, city, state, zip,zip_4, area_code, phone, salary, birthdate, hiredate,title, dept_no, mgr, region, division, total_sales)
  2                values (9,"Bar","Candi","C","400 East Street","Yorken","NY","99999","9999","220","321-9999",12.00,"10-oct-1933","15-jan-1969","Sales Representative",3,5,100,10,35000);
1 row created.
SQL>
SQL>   select lastname, firstname, salary
  2    from (SELECT lastname, firstname, salary FROM employee ORDER BY salary DESC)
  3    where rownum <= 3 ;
LASTNAME             FIRSTNAME           SALARY
-------------------- --------------- ----------
Will                 Robin                   25
Bush                 Dave                    22
Horry                Tedi                    13
3 rows selected.
SQL>
SQL> drop table employee;
Table dropped.
SQL>
SQL>
SQL> --



Retrieving the Top Five Students with ROWNUM

   
SQL>
SQL> CREATE TABLE SAT (
  2     StudentID  INT NOT NULL,
  3     ExamID     INT NOT NULL,
  4     Mark       INT,
  5     IfPassed   SMALLINT,
  6     Comments   VARCHAR(255),
  7     CONSTRAINT PK_SAT PRIMARY KEY (StudentID, ExamID));
Table created.
SQL>
SQL>
SQL> INSERT INTO SAT (StudentID,ExamID,Mark,IfPassed,Comments) VALUES (1,1,55,1,"Satisfactory");
1 row created.
SQL> INSERT INTO SAT (StudentID,ExamID,Mark,IfPassed,Comments) VALUES (1,2,73,1,"Good result");
1 row created.
SQL> INSERT INTO SAT (StudentID,ExamID,Mark,IfPassed,Comments) VALUES (2,3,44,1,"Hard");
1 row created.
SQL> INSERT INTO SAT (StudentID,ExamID,Mark,IfPassed,Comments) VALUES (2,5,39,0,"Simple");
1 row created.
SQL> INSERT INTO SAT (StudentID,ExamID,Mark,IfPassed) VALUES (2,6,63,1);
1 row created.
SQL>
SQL>
SQL> SELECT StudentID, AverageMark FROM (
  2     SELECT StudentID, AVG(Mark) AS AverageMark
  3     FROM SAT
  4     GROUP BY StudentID
  5     ORDER BY AverageMark DESC
  6  )
  7  WHERE ROWNUM <= 5;
 STUDENTID AVERAGEMARK
---------- -----------
         1          64
         2  48.6666667
2 rows selected.
SQL>
SQL> drop table SAT;
Table dropped.
SQL>



Use rownum = 1 and select into

   
SQL>
SQL>
SQL>
SQL> CREATE TABLE EMP(
  2      EMPNO NUMBER(4) NOT NULL,
  3      ENAME VARCHAR2(10),
  4      JOB VARCHAR2(9),
  5      MGR NUMBER(4),
  6      HIREDATE DATE,
  7      SAL NUMBER(7, 2),
  8      COMM NUMBER(7, 2),
  9      DEPTNO NUMBER(2)
 10  );
Table created.
SQL>
SQL> INSERT INTO EMP VALUES(7369, "SMITH", "CLERK", 7902,TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(7499, "ALLEN", "SALESMAN", 7698,TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7521, "WARD", "SALESMAN", 7698,TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7566, "JONES", "MANAGER", 7839,TO_DATE("2-APR-1981", "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES(7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES(7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES(7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES(7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
1 row created.
SQL>
SQL> CREATE TABLE DEPT(
  2      DEPTNO NUMBER(2),
  3      DNAME VARCHAR2(14),
  4      LOC VARCHAR2(13)
  5  );
Table created.
SQL>
SQL> INSERT INTO DEPT VALUES (10, "ACCOUNTING", "NEW YORK");
1 row created.
SQL> INSERT INTO DEPT VALUES (20, "RESEARCH", "DALLAS");
1 row created.
SQL> INSERT INTO DEPT VALUES (30, "SALES", "CHICAGO");
1 row created.
SQL> INSERT INTO DEPT VALUES (40, "OPERATIONS", "BOSTON");
1 row created.
SQL>
SQL> declare
  2      l_ename  emp.ename%type;
  3  begin
  4      for x in (select deptno, dname from dept order by deptno)
  5      loop
  6          begin
  7             select ename into l_ename
  8               from emp
  9              where deptno = x.deptno
 10                and sal = (select max(sal)from emp where deptno = x.deptno)
 11             and rownum = 1;
 12          exception when no_data_found
 13          then
 14              l_ename := "(none)";
 15          end;
 16          dbms_output.put_line( x.deptno || ", " || x.dname || ", " || l_ename );
 17      end loop;
 18  end;
 19  /
PL/SQL procedure successfully completed.
SQL>
SQL> drop table dept;
Table dropped.
SQL> drop table emp;
Table dropped.
SQL>



Use rownum column with order by

   
SQL>
SQL> CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
  2                    ENAME VARCHAR2(10),
  3                    JOB VARCHAR2(9),
  4                    MGR NUMBER(4),
  5                    HIREDATE DATE,
  6                    SAL NUMBER(7, 2),
  7                    COMM NUMBER(7, 2),
  8                    DEPTNO NUMBER(2));
Table created.
SQL>
SQL> INSERT INTO EMP VALUES (7369, "SMITH", "CLERK",    7902, TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7499, "ALLEN", "SALESMAN", 7698, TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7521, "WARD",  "SALESMAN", 7698, TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7566, "JONES", "MANAGER",  7839, TO_DATE("2-APR-1981",  "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
1 row created.
SQL>
SQL> CREATE TABLE DEPT (DEPTNO NUMBER(2),DNAME VARCHAR2(14),LOC VARCHAR2(13) );
Table created.
SQL>
SQL> INSERT INTO DEPT VALUES (10, "ACCOUNTING", "NEW YORK");
1 row created.
SQL> INSERT INTO DEPT VALUES (20, "RESEARCH", "DALLAS");
1 row created.
SQL> INSERT INTO DEPT VALUES (30, "SALES", "CHICAGO");
1 row created.
SQL> INSERT INTO DEPT VALUES (40, "OPERATIONS", "BOSTON");
1 row created.
SQL>
SQL> select rownum, ename, hiredate
  2  from emp
  3  order by hiredate;
    ROWNUM ENAME      HIREDATE
---------- ---------- ---------
         1 SMITH      17-DEC-80
         2 ALLEN      20-FEB-81
         3 WARD       22-FEB-81
         4 JONES      02-APR-81
         6 BLAKE      01-MAY-81
         7 CLARK      09-JUN-81
        10 TURNER     08-SEP-81
         5 MARTIN     28-SEP-81
         9 KING       17-NOV-81
        12 JAMES      03-DEC-81
        13 FORD       03-DEC-81
    ROWNUM ENAME      HIREDATE
---------- ---------- ---------
        14 MILLER     23-JAN-82
         8 SCOTT      09-DEC-82
        11 ADAMS      12-JAN-83
14 rows selected.
SQL>
SQL> drop table emp cascade constraints;
Table dropped.
SQL> drop table dept cascade constraints;
Table dropped.
SQL>



Use rownum in select clause

   
SQL>
SQL> CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
  2                    ENAME VARCHAR2(10),
  3                    JOB VARCHAR2(9),
  4                    MGR NUMBER(4),
  5                    HIREDATE DATE,
  6                    SAL NUMBER(7, 2),
  7                    COMM NUMBER(7, 2),
  8                    DEPTNO NUMBER(2));
Table created.
SQL>
SQL> INSERT INTO EMP VALUES (7369, "SMITH", "CLERK",    7902, TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7499, "ALLEN", "SALESMAN", 7698, TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7521, "WARD",  "SALESMAN", 7698, TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7566, "JONES", "MANAGER",  7839, TO_DATE("2-APR-1981",  "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
1 row created.
SQL>
SQL> select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 09-DEC-82       3000                    20

                                                                                                                                      Page           1
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 12-JAN-83       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10


                                                                                                                                      Page           2
14 rows selected.
SQL>
SQL> SELECT ROWNUM, ename
  2  FROM   emp
  3  WHERE  ROWNUM < 6
  4  ORDER BY ename;
    ROWNUM ENAME
---------- ----------
         2 ALLEN
         4 JONES
         5 MARTIN
         1 SMITH
         3 WARD


                                                                                                                                      Page           1
SQL>
SQL> drop table emp;
Table dropped.



Use rownum in update set statement

   
SQL>
SQL> CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
  2                    ENAME VARCHAR2(10),
  3                    JOB VARCHAR2(9),
  4                    MGR NUMBER(4),
  5                    HIREDATE DATE,
  6                    SAL NUMBER(7, 2),
  7                    COMM NUMBER(7, 2),
  8                    DEPTNO NUMBER(2));
Table created.
SQL>
SQL> INSERT INTO EMP VALUES (7369, "SMITH", "CLERK",    7902, TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7499, "ALLEN", "SALESMAN", 7698, TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7521, "WARD",  "SALESMAN", 7698, TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7566, "JONES", "MANAGER",  7839, TO_DATE("2-APR-1981",  "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
1 row created.
SQL>
SQL> select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 09-DEC-82       3000                    20

                                                                                                                                      Page           1
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 12-JAN-83       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10


                                                                                                                                      Page           2
14 rows selected.
SQL>
SQL> UPDATE emp
  2  SET    empno  = ROWNUM;
14 rows updated.
SQL>
SQL> select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
         1 SMITH      CLERK           7902 17-DEC-80        800                    20
         2 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
         3 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
         4 JONES      MANAGER         7839 02-APR-81       2975                    20
         5 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
         6 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
         7 CLARK      MANAGER         7839 09-JUN-81       2450                    10
         8 SCOTT      ANALYST         7566 09-DEC-82       3000                    20

                                                                                                                                      Page           1
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
         9 KING       PRESIDENT            17-NOV-81       5000                    10
        10 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
        11 ADAMS      CLERK           7788 12-JAN-83       1100                    20
        12 JAMES      CLERK           7698 03-DEC-81        950                    30
        13 FORD       ANALYST         7566 03-DEC-81       3000                    20
        14 MILLER     CLERK           7782 23-JAN-82       1300                    10


                                                                                                                                      Page           2
14 rows selected.
SQL>
SQL>
SQL> drop table emp;
Table dropped.



Use rownum in where clause to control the row count

   
SQL>
SQL> CREATE TABLE EMP (EMPNO NUMBER(4) NOT NULL,
  2                    ENAME VARCHAR2(10),
  3                    JOB VARCHAR2(9),
  4                    MGR NUMBER(4),
  5                    HIREDATE DATE,
  6                    SAL NUMBER(7, 2),
  7                    COMM NUMBER(7, 2),
  8                    DEPTNO NUMBER(2));
Table created.
SQL>
SQL> INSERT INTO EMP VALUES (7369, "SMITH", "CLERK",    7902, TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7499, "ALLEN", "SALESMAN", 7698, TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7521, "WARD",  "SALESMAN", 7698, TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7566, "JONES", "MANAGER",  7839, TO_DATE("2-APR-1981",  "DD-MON-YYYY"), 2975, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
1 row created.
SQL> INSERT INTO EMP VALUES (7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
1 row created.
SQL> INSERT INTO EMP VALUES (7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
1 row created.
SQL> INSERT INTO EMP VALUES (7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
1 row created.
SQL>
SQL> select * from emp;
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7369 SMITH      CLERK           7902 17-DEC-80        800                    20
      7499 ALLEN      SALESMAN        7698 20-FEB-81       1600        300         30
      7521 WARD       SALESMAN        7698 22-FEB-81       1250        500         30
      7566 JONES      MANAGER         7839 02-APR-81       2975                    20
      7654 MARTIN     SALESMAN        7698 28-SEP-81       1250       1400         30
      7698 BLAKE      MANAGER         7839 01-MAY-81       2850                    30
      7782 CLARK      MANAGER         7839 09-JUN-81       2450                    10
      7788 SCOTT      ANALYST         7566 09-DEC-82       3000                    20

                                                                                                                                      Page           1
     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM     DEPTNO
---------- ---------- --------- ---------- --------- ---------- ---------- ----------
      7839 KING       PRESIDENT            17-NOV-81       5000                    10
      7844 TURNER     SALESMAN        7698 08-SEP-81       1500          0         30
      7876 ADAMS      CLERK           7788 12-JAN-83       1100                    20
      7900 JAMES      CLERK           7698 03-DEC-81        950                    30
      7902 FORD       ANALYST         7566 03-DEC-81       3000                    20
      7934 MILLER     CLERK           7782 23-JAN-82       1300                    10


                                                                                                                                      Page           2
14 rows selected.
SQL>
SQL>
SQL> SELECT ROWID, empno
  2  FROM   emp
  3  WHERE  ROWNUM < 6;
ROWID                   EMPNO
------------------ ----------
AAADc4AABAAAKUaAAA       7369
AAADc4AABAAAKUaAAB       7499
AAADc4AABAAAKUaAAC       7521
AAADc4AABAAAKUaAAD       7566
AAADc4AABAAAKUaAAE       7654


                                                                                                                                      Page           1
SQL>
SQL>
SQL> drop table emp;
Table dropped.
SQL>



Use rownum in where clause to limit the row count

   
SQL>
SQL> CREATE TABLE departments
  2  (department_id           number(10)            not null,
  3   department_name      varchar2(50)      not null,
  4   CONSTRAINT departments_pk PRIMARY KEY (department_id)
  5  );
Table created.
SQL>
SQL>
SQL>
SQL> insert into departments ( department_id, department_name )
  2                    values( 1,             "Data Group" );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
  2                    values( 2,             "Purchasing" );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
  2                    values( 3,             "Call Center" );
1 row created.
SQL>
SQL> insert into departments ( department_id, department_name )
  2                    values( 4,             "Communication" );
1 row created.
SQL>
SQL>
SQL>  select department_name, upper( department_name )
  2      from departments
  3     where rownum < 2
  4     order by department_name
  5    /
DEPARTMENT_NAME
--------------------------------------------------
UPPER(DEPARTMENT_NAME)
--------------------------------------------------
Data Group
DATA GROUP

1 row selected.
SQL>
SQL> drop table departments;
Table dropped.
SQL>
SQL>
SQL> --



Use rownum to limit the subquery

   
SQL>
SQL> create table emp(
  2           emp_no                 integer         primary key,
  3           lastname               varchar2(20)    not null,
  4           firstname              varchar2(15)    not null,
  5           midinit                varchar2(1),
  6           street                 varchar2(30),
  7           city                   varchar2(20),
  8           state                  varchar2(2),
  9           zip                    varchar2(5),
 10           shortZipCode                   varchar2(4),
 11           area_code              varchar2(3),
 12           phone                  varchar2(8),
 13           salary                 number(5,2),
 14           birthdate              date,
 15           startDate              date,
 16           title                  varchar2(20),
 17           dept_no                integer         ,
 18           mgr                    integer,
 19           region                 number,
 20           division               number,
 21           total_sales            number
 22  );
Table created.
SQL> -- emp Table Inserts:
SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, birthdate, title)values
  2                      (1,"Z","Joy","R","1 Ave","New York","NY","12122","2333","212","200-1111","12-nov-1976","President");
1 row created.
SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, salary, birthdate, startDate,title, dept_no, mgr, region, division, total_sales)valu
es
  2                      (2,"X","Lucy","J","1 Street","New York","NY","43552","6633","212","234-4444",7.75,"21-mar-1976","1-feb-1994","Sales Manager",2,1,100,10,40000);
1 row created.
SQL> insert into emp(emp_no, lastname, firstname, midinit, street, city, state, zip,shortZipCode, area_code, phone, salary, birthdate, startDate,title, dept_no, mgr, region, division, total_sales)valu
es
  2                      (3,"Y","Jordan","E","1 Drive","New York","NY","76822","8763","212","222-2222",7.75,"14-feb-1963","15-mar-1995","Sales Clerk",2,2,100,10,10000);
1 row created.
SQL>
SQL> select lastname, firstname, salary
  2    from (SELECT lastname, firstname, salary FROM emp ORDER BY salary DESC)
  3   where rownum <= 3 ;
LASTNAME             FIRSTNAME           SALARY
-------------------- --------------- ----------
Z                    Joy
X                    Lucy                  7.75
Y                    Jordan                7.75
SQL>
SQL> drop table emp;
Table dropped.