Oracle PL/SQL Tutorial/View/Update View

Query a view with condition

SQL>
SQL>
SQL> create table registrations
  2  ( attendee    NUMBER(4)
  3  , course      VARCHAR2(6)
  4  , begindate   DATE
  5  , evaluation  NUMBER(1)) ;
Table created.
SQL>
SQL>
SQL> insert into registrations values (1, "SQL",date "1999-04-12",4   );
1 row created.
SQL> insert into registrations values (2, "SQL",date "1999-12-13",NULL);
1 row created.
SQL> insert into registrations values (3, "SQL",date "1999-12-13",NULL);
1 row created.
SQL> insert into registrations values (4, "OAU",date "1999-08-10",4   );
1 row created.
SQL> insert into registrations values (5, "OAU",date "2000-09-27",5   );
1 row created.
SQL> insert into registrations values (6, "JAV",date "1999-12-13",2   );
1 row created.
SQL> insert into registrations values (7, "JAV",date "2000-02-01",4   );
1 row created.
SQL> insert into registrations values (8, "JAV",date "2000-02-01",5   );
1 row created.
SQL> insert into registrations values (9, "XML",date "2000-02-03",4   );
1 row created.
SQL> insert into registrations values (10,"XML",date "2000-02-03",5   );
1 row created.
SQL> insert into registrations values (1, "PLS",date "2000-09-11",NULL);
1 row created.
SQL> insert into registrations values (2, "PLS",date "2000-09-11",NULL);
1 row created.
SQL> insert into registrations values (3, "PLS",date "2000-09-11",NULL);
1 row created.
SQL>
SQL>
SQL>
SQL> create or replace view avg_evaluations as
  2  select course
  3  ,      avg(evaluation) as avg_eval
  4  from   registrations
  5  group  by course;
View created.
SQL>
SQL>
SQL> select *
  2  from   avg_evaluations
  3  where  avg_eval >= 4;
COURSE AVG_EVAL
------ --------
OAU           5
XML           5
SQL           4
3 rows selected.
SQL>
SQL> drop table registrations;
Table dropped.
SQL>
SQL>

Update a view

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> create or replace view dept20_v as
  2  select * from employees where deptno=20;
View created.
SQL>
SQL>
SQL>
SQL> update dept20_v
  2  set    deptno = 30
  3  where  job    = "TRAINER";
0 rows updated.
SQL>
SQL> drop table employees;
Table dropped.
SQL>
SQL>