First three rows from subquery : Virtual Table « Subquery « Oracle PL / SQL

1. Oracle PL / SQL
2. Subquery
3. Virtual Table

First three rows from subquery

 
SQL>
SQL> create table history
  2  ( empno      NUMBER(4)
  3  , beginyear  NUMBER(4)
  4  , begindate  DATE
  5  , enddate    DATE
  6  , deptno     NUMBER(2)
  7  , sal        NUMBER(6,2)
  8  , comments   VARCHAR2(60)
  9  , constraint H_PK         primary key (empno,begindate)
 10  , constraint H_BEG_END    check       (begindate < enddate)
 11  ) ;

Table created.

SQL>
SQL>
SQL> alter session  set NLS_DATE_FORMAT='DD-MM-YYYY';

Session altered.

SQL>
SQL> insert into history values (1,2000,'01-02-2000', NULL       ,20, 800,'restarted');

1 row created.

SQL> insert into history values (2,1995,'01-10-1995','01-11-2009',30,1700,'');

1 row created.

SQL> insert into history values (2,2009,'01-11-2009', NULL       ,30,1600,'just hired');

1 row created.

SQL> insert into history values (3,1986,'01-10-1986','01-08-1987',20,1000,'');

1 row created.

SQL> insert into history values (3,1987,'01-08-1987','01-01-1989',30,1000,'On training');

1 row created.

SQL> insert into history values (3,2000,'01-02-2000', NULL       ,30,1250,'');

1 row created.

SQL>
SQL> select *
  2  from  (select empno, sal
  3         from   history
  4         order  by sal desc)
  5  where  rownum <= 3;

     EMPNO        SAL
---------- ----------
         2       1700
         2       1600
         3       1250

SQL>
SQL> drop table history;

Table dropped.

SQL>

   
  

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