Oracle PL/SQL Tutorial/View/Create View

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a user-defined type view

SQL>
SQL>
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>
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>
SQL>
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> create or replace type emp_type
  2  as object
  3  (empno       number(4),
  4   ename       varchar2(10),
  5   job         varchar2(9),
  6   mgr         number(4),
  7   hiredate    date,
  8   sal         number(7, 2),
  9   comm        number(7, 2)
 10  );
 11  /
Type created.
SQL>
SQL>
SQL> create or replace type emp_tab_type
  2  as table of emp_type
  3  /
Type created.
SQL>
SQL>
SQL> create or replace type dept_type
  2  as object
  3  ( deptno number(2),
  4    dname  varchar2(14),
  5    loc    varchar2(13),
  6    emps   emp_tab_type
  7  )
  8  /
Type created.
SQL>
SQL> create or replace view dept_or
  2  of dept_type
  3  with object identifier(deptno)
  4  as
  5  select deptno, dname, loc,
  6         cast ( multiset (
  7                 select empno, ename, job, mgr, hiredate, sal, comm
  8                   from emp
  9                  where emp.deptno = dept.deptno )
 10                as emp_tab_type )
 11    from dept
 12  /
View created.
SQL>
SQL> declare
  2     l_emps  emp_tab_type;
  3  begin
  4      select p.emps into l_emps from dept_or p where deptno = 10;
  5
  6      for i in 1 .. l_emps.count
  7      loop
  8          l_emps(i).ename := lower(l_emps(i).ename);
  9      end loop;
 10
 11      update dept_or set emps = l_emps where deptno = 10;
 12  end;
 13  /
declare
*
ERROR at line 1:
ORA-01733: virtual column not allowed here
ORA-06512: at line 11

SQL>
SQL> drop type dept_type;
Type dropped.
SQL>
SQL> drop type emp_tab_type;
Type dropped.
SQL>
SQL> drop type emp_type;
Type dropped.
SQL>
SQL> drop table emp;
Table dropped.
SQL>
SQL> drop table dept;
Table dropped.


Choose specific column from base table

SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
  3  /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL> CREATE VIEW employee_view AS
  2  SELECT id, first_name, last_name
  3  FROM employee;
View created.
SQL>
SQL> select * from employee_view;
ID   FIRST_NAME LAST_NAME
---- ---------- ----------
01   Jason      Martin
02   Alison     Mathews
03   James      Smith
04   Celia      Rice
05   Robert     Black
06   Linda      Green
07   David      Larry
08   James      Cat
8 rows selected.
SQL>
SQL> drop view employee_view;
View dropped.
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>


Create a view by joining two tables

SQL>
SQL>
SQL> create table courses
  2  ( code        VARCHAR2(6)
  3  , description VARCHAR2(30)
  4  , category    CHAR(3)
  5  , duration    NUMBER(2)) ;
Table created.
SQL>
SQL>
SQL> insert into courses values("SQL","SQL course",    "GEN",4);
1 row created.
SQL> insert into courses values("OAU","Oracle course", "GEN",1);
1 row created.
SQL> insert into courses values("JAV","Java course",   "BLD",4);
1 row created.
SQL> insert into courses values("PLS","PL/SQL course", "BLD",1);
1 row created.
SQL> insert into courses values("XML","XML course",    "BLD",2);
1 row created.
SQL> insert into courses values("ERM","ERM course",    "DSG",3);
1 row created.
SQL> insert into courses values("PMT","UML course",    "DSG",1);
1 row created.
SQL> insert into courses values("RSD","C# course",     "DSG",2);
1 row created.
SQL> insert into courses values("PRO","C++ course",    "DSG",5);
1 row created.
SQL> insert into courses values("GEN","GWT course",    "DSG",4);
1 row created.
SQL>
SQL>
SQL>
SQL> create table course_schedule
  2  ( course     VARCHAR2(6)
  3  , begindate  DATE
  4  , trainer    NUMBER(4)
  5  , location   VARCHAR2(20)) ;
Table created.
SQL>
SQL>
SQL> insert into course_schedule values ("SQL",date "1999-04-12",1,"VANCOUVER" );
1 row created.
SQL> insert into course_schedule values ("OAU",date "1999-08-10",2,"CHICAGO");
1 row created.
SQL> insert into course_schedule values ("SQL",date "1999-10-04",3,"SEATTLE");
1 row created.
SQL> insert into course_schedule values ("SQL",date "1999-12-13",4,"DALLAS" );
1 row created.
SQL> insert into course_schedule values ("JAV",date "1999-12-13",5,"SEATTLE");
1 row created.
SQL> insert into course_schedule values ("XML",date "2000-02-03",6,"VANCOUVER" );
1 row created.
SQL> insert into course_schedule values ("JAV",date "2000-02-01",7,"DALLAS" );
1 row created.
SQL> insert into course_schedule values ("PLS",date "2000-09-11",8,"VANCOUVER" );
1 row created.
SQL> insert into course_schedule values ("XML",date "2000-09-18",NULL,"SEATTLE");
1 row created.
SQL> insert into course_schedule values ("OAU",date "2000-09-27",9,"DALLAS" );
1 row created.
SQL> insert into course_schedule values ("ERM",date "2001-01-15",10, NULL    );
1 row created.
SQL> insert into course_schedule values ("PRO",date "2001-02-19",NULL,"VANCOUVER" );
1 row created.
SQL> insert into course_schedule values ("RSD",date "2001-02-24",8,"CHICAGO");
1 row created.
SQL>
SQL>
SQL> create or replace view crs_course_schedule as
  2  select o.course as course_code, c.description, o.begindate
  3  from   course_schedule o
  4         join
  5         courses   c
  6         on (o.course = c.code);
View created.
SQL>
SQL> drop table course_schedule;
Table dropped.
SQL>
SQL> drop table courses;
Table dropped.
SQL>
SQL>


create materialized view emp_dept build immediate refresh on demand enable query rewrite

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  );
SQL>
SQL> INSERT INTO EMP VALUES(7369, "SMITH", "CLERK", 7902,TO_DATE("17-DEC-1980", "DD-MON-YYYY"), 800, NULL, 20);
SQL> INSERT INTO EMP VALUES(7499, "ALLEN", "SALESMAN", 7698,TO_DATE("20-FEB-1981", "DD-MON-YYYY"), 1600, 300, 30);
SQL> INSERT INTO EMP VALUES(7521, "WARD", "SALESMAN", 7698,TO_DATE("22-FEB-1981", "DD-MON-YYYY"), 1250, 500, 30);
SQL> INSERT INTO EMP VALUES(7566, "JONES", "MANAGER", 7839,TO_DATE("2-APR-1981", "DD-MON-YYYY"), 2975, NULL, 20);
SQL> INSERT INTO EMP VALUES(7654, "MARTIN", "SALESMAN", 7698,TO_DATE("28-SEP-1981", "DD-MON-YYYY"), 1250, 1400, 30);
SQL> INSERT INTO EMP VALUES(7698, "BLAKE", "MANAGER", 7839,TO_DATE("1-MAY-1981", "DD-MON-YYYY"), 2850, NULL, 30);
SQL> INSERT INTO EMP VALUES(7782, "CLARK", "MANAGER", 7839,TO_DATE("9-JUN-1981", "DD-MON-YYYY"), 2450, NULL, 10);
SQL> INSERT INTO EMP VALUES(7788, "SCOTT", "ANALYST", 7566,TO_DATE("09-DEC-1982", "DD-MON-YYYY"), 3000, NULL, 20);
SQL> INSERT INTO EMP VALUES(7839, "KING", "PRESIDENT", NULL,TO_DATE("17-NOV-1981", "DD-MON-YYYY"), 5000, NULL, 10);
SQL> INSERT INTO EMP VALUES(7844, "TURNER", "SALESMAN", 7698,TO_DATE("8-SEP-1981", "DD-MON-YYYY"), 1500, 0, 30);
SQL> INSERT INTO EMP VALUES(7876, "ADAMS", "CLERK", 7788,TO_DATE("12-JAN-1983", "DD-MON-YYYY"), 1100, NULL, 20);
SQL> INSERT INTO EMP VALUES(7900, "JAMES", "CLERK", 7698,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 950, NULL, 30);
SQL> INSERT INTO EMP VALUES(7902, "FORD", "ANALYST", 7566,TO_DATE("3-DEC-1981", "DD-MON-YYYY"), 3000, NULL, 20);
SQL> INSERT INTO EMP VALUES(7934, "MILLER", "CLERK", 7782,TO_DATE("23-JAN-1982", "DD-MON-YYYY"), 1300, NULL, 10);
SQL>
SQL> CREATE TABLE DEPT(
  2      DEPTNO NUMBER(2),
  3      DNAME VARCHAR2(14),
  4      LOC VARCHAR2(13)
  5  );
SQL>
SQL> INSERT INTO DEPT VALUES (10, "ACCOUNTING", "NEW YORK");
SQL> INSERT INTO DEPT VALUES (20, "RESEARCH", "DALLAS");
SQL> INSERT INTO DEPT VALUES (30, "SALES", "CHICAGO");
SQL> INSERT INTO DEPT VALUES (40, "OPERATIONS", "BOSTON");
SQL>
SQL> create materialized view emp_dept
  2  build immediate
  3  refresh on demand
  4  enable query rewrite
  5  as
  6  select dept.deptno, dept.dname, count (*)
  7    from emp, dept
  8   where emp.deptno = dept.deptno
  9   group by dept.deptno, dept.dname
 10  /

SQL>
SQL> begin
  2      dbms_stats.set_table_stats( user, "EMP", numrows => 100000 );
  3      dbms_stats.set_table_stats( user, "DEPT", numrows =>  1000 );
  4  end;
  5  /
SQL>
SQL>
SQL> drop table emp;
SQL>
SQL> drop table dept;


CREATE MATERIALIZED VIEW with rowid

SQL> -- create demo table
SQL> create table emp(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    fname         VARCHAR2(10 BYTE),
  4    lname          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL> CREATE MATERIALIZED VIEW LOG ON emp
  2    WITH ROWID (fname)
  3    INCLUDING NEW VALUES;
Materialized view log created.
SQL>
SQL>
SQL> drop table emp;
Table dropped.
SQL>


CREATE MATERIALIZED VIEW with TABLESPACE

SQL> create table emp(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    fname         VARCHAR2(10 BYTE),
  4    lname          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> CREATE MATERIALIZED VIEW LOG ON emp
  2    PCTFREE 5
  3    TABLESPACE mv_logs
  4    STORAGE (INITIAL 1M NEXT 1M) WITH ROWID;
SQL>
SQL>
SQL> drop view log;
SQL>
SQL> drop table emp;
Table dropped.


Create view based on aggregate function

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> drop table registrations;
Table dropped.
SQL>
SQL>


Create view based on user-defined function

SQL>
SQL>
SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
  3  /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME           LAST_NAME            START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- -------------------- -------------------- --------- --------- ---------- ---------- ---------------
01   Jason                Martin               25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison               Mathews              21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James                Smith                12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia                Rice                 24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert               Black                15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda                Green                30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David                Larry                31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James                Cat                  17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL>
SQL> create or replace function f_emp_dsp (i_empNo VARCHAR)
  2  return VARCHAR2 is v_out VARCHAR2 (256);
  3  begin
  4      DBMS_OUTPUT.put_line("Inside of F_EMP_DSP");
  5      select initcap(first_name)||": "||initcap(last_name)
  6        into v_out from employee where id = i_empNo;
  7      return v_out;
  8  end f_emp_dsp;
  9  /
Function created.
SQL>
SQL> create or replace view v_emp as
  2  select f_emp_dsp(id) emp_dsp
  3  from employee;
View created.
SQL> /
View created.
SQL>
SQL> select * from v_emp;
EMP_DSP
--------------------------------------------------------------------------
Jason: Martin
Alison: Mathews
James: Smith
Celia: Rice
Robert: Black
Linda: Green
David: Larry
James: Cat
8 rows selected.
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
Inside of F_EMP_DSP
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>


Create view by join three tables

SQL> create table emp
  2  ( empno      NUMBER(4)    constraint E_PK primary key
  3  , ename      VARCHAR2(8)
  4  , init       VARCHAR2(5)
  5  , job        VARCHAR2(8)
  6  , mgr        NUMBER(4)
  7  , bdate      DATE
  8  , sal        NUMBER(6,2)
  9  , comm       NUMBER(6,2)
 10  , deptno     NUMBER(2)    default 10
 11  ) ;
Table created.
SQL> insert into emp values(1,"Tom","N",   "TRAINER", 13,date "1965-12-17",  800 , NULL,  20);
1 row created.
SQL> insert into emp values(2,"Jack","JAM", "Tester",6,date "1961-02-20",  1600, 300,   30);
1 row created.
SQL> insert into emp values(3,"Wil","TF" ,  "Tester",6,date "1962-02-22",  1250, 500,   30);
1 row created.
SQL> insert into emp values(4,"Jane","JM",  "Designer", 9,date "1967-04-02",  2975, NULL,  20);
1 row created.
SQL> insert into emp values(5,"Mary","P",  "Tester",6,date "1956-09-28",  1250, 1400,  30);
1 row created.
SQL> insert into emp values(6,"Black","R",   "Designer", 9,date "1963-11-01",  2850, NULL,  30);
1 row created.
SQL> insert into emp values(7,"Chris","AB",  "Designer", 9,date "1965-06-09",  2450, NULL,  10);
1 row created.
SQL> insert into emp values(8,"Smart","SCJ", "TRAINER", 4,date "1959-11-26",  3000, NULL,  20);
1 row created.
SQL> insert into emp values(9,"Peter","CC",   "Designer",NULL,date "1952-11-17",  5000, NULL,  10);
1 row created.
SQL> insert into emp values(10,"Take","JJ", "Tester",6,date "1968-09-28",  1500, 0,     30);
1 row created.
SQL> insert into emp values(11,"Ana","AA",  "TRAINER", 8,date "1966-12-30",  1100, NULL,  20);
1 row created.
SQL> insert into emp values(12,"Jane","R",   "Manager",   6,date "1969-12-03",  800 , NULL,  30);
1 row created.
SQL> insert into emp values(13,"Fake","MG",   "TRAINER", 4,date "1959-02-13",  3000, NULL,  20);
1 row created.
SQL> insert into emp values(14,"Mike","TJA","Manager",   7,date "1962-01-23",  1300, NULL,  10);
1 row created.
SQL>
SQL> create table departments
  2  ( deptno NUMBER(2)     constraint D_PK primary key
  3  , dname  VARCHAR2(10)
  4  , location VARCHAR2(8)
  5  , mgr    NUMBER(4)
  6  ) ;
Table created.
SQL>
SQL> insert into departments values (10,"ACCOUNTING","NEW YORK",7);
1 row created.
SQL> insert into departments values (20,"TRAINING",  "DALLAS",  4);
1 row created.
SQL> insert into departments values (30,"SALES",     "CHICAGO", 6);
1 row created.
SQL> insert into departments values (40,"HR",        "BOSTON",  9);
1 row created.
SQL>
SQL> create view empdept_v as
  2  select e.empno
  3  ,      e.ENAME
  4  ,      e.init
  5  ,      d.dname
  6  ,      d.location
  7  ,      m.ENAME    as Designer
  8  from   emp   e
  9         join
 10         departments d using (deptno)
 11         join
 12         emp   m on (m.empno = d.mgr);

SQL> drop table emp;
Table dropped.
SQL> drop table departments;
Table dropped.


Create view on single field of a type

SQL> create type addressType as object
  2  (Street   VARCHAR2(50),
  3  City      VARCHAR2(25),
  4  State     CHAR(2),
  5  Zip       NUMBER);
  6  /
SQL>
SQL> create type personType as object
  2  (Name     VARCHAR2(25),
  3   Address  addressType);
  4  /
SQL>
SQL>
SQL> create or replace type personType as object
  2  (Name     VARCHAR2(25),
  3   Address  addressType);
  4  /
SQL>
SQL>
SQL> create table myemp
  2  (cid    NUMBER,
  3   Person         personType);
SQL>
SQL>
SQL> insert into myemp values(1,personType("SomeName",addressType("StreetValue","CityValue","ST",11111)));
SQL>
SQL>
SQL> create index empview
  2  on myemp(Person.Address.City);
SQL>
SQL>
SQL> drop table myemp;
SQL> drop type personType;
SQL> drop type addressType;
SQL>
SQL>
SQL>
SQL>


Creating and Using a View

You create a view using CREATE VIEW , which has the following simplified syntax:



CREATE [OR REPLACE] VIEW [{FORCE | NOFORCE}] VIEW view_name
[(alias_name[, alias_name...])] AS subquery
[WITH {CHECK OPTION | READ ONLY} CONSTRAINT constraint_name];


where

  1. OR REPLACE specifies the view is to replace an existing view if present.
  2. FORCE specifies the view is to be created even if the base tables don"t exist.
  3. NOFORCE specifies the view is not to be created if the base tables don"t exist; NOFORCE is the default.
  4. alias_name specifies the name of an alias for an expression in the subquery.
  5. There must be the same number of aliases as there are expressions in the subquery.
  6. subquery specifies the subquery that retrieves from the base tables.
  7. If you"ve supplied aliases, you can use those aliases in the list after the SELECT clause.
  8. WITH CHECK OPTION specifies that only the rows that would be retrieved by the subquery can be inserted, updated, or deleted.
  9. By default, rows are not checked that they are retrievable by the subquery before they are inserted, updated, or deleted.
  10. constraint_name specifies the name of the WITH CHECK OPTION or READ ONLY constraint.
  11. WITH READ ONLY specifies that rows may only read from the base tables.

There are two basic types of views:

Simple views, which contain a subquery that retrieves from one base table

Complex views, which contain a subquery that:

  1. Retrieves from multiple base tables
  2. Groups rows using a GROUP BY or DISTINCT clause
  3. Contains a function call

Quote from:

Oracle Database 10g SQL (Osborne ORACLE Press Series) (Paperback)

# Paperback: 608 pages

# Publisher: McGraw-Hill Osborne Media; 1st edition (February 20, 2004)

# Language: English

# ISBN-10: 0072229810

# ISBN-13: 978-0072229813

Creating and Using Simple Views

Simple views access one base table.



SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
  3  /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL> CREATE VIEW my_view AS
  2  SELECT *
  3  FROM employee
  4  WHERE id < 5;
View created.
SQL>
SQL> select * from my_view;
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
SQL>
SQL> drop view my_view;
View dropped.
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>
SQL>
SQL>


Creating a View with a CHECK OPTION Constraint

You can specify that DML operations on a view must satisfy the subquery by adding a CHECK OPTION constraint to the view.



SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
  3  /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL> CREATE VIEW myView AS
  2  SELECT *
  3  FROM employee
  4  WHERE id < 5
  5  WITH CHECK OPTION CONSTRAINT myView;
View created.
SQL>
SQL> INSERT INTO myView (id) VALUES (0);
1 row created.
SQL>
SQL> INSERT INTO myView (id) VALUES (7);
INSERT INTO myView (id) VALUES (7)
            *
ERROR at line 1:
ORA-01402: view WITH CHECK OPTION where-clause violation

SQL>
SQL> select * from myView;
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
0
SQL>
SQL> drop view myView;
View dropped.
SQL>
SQL>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>
SQL>


Creating a View with a READ ONLY Constraint

You can make a view read only by adding a READ ONLY constraint to the view.



SQL> -- create demo table
SQL> create table Employee(
  2    ID                 VARCHAR2(4 BYTE)         NOT NULL,
  3    First_Name         VARCHAR2(10 BYTE),
  4    Last_Name          VARCHAR2(10 BYTE),
  5    Start_Date         DATE,
  6    End_Date           DATE,
  7    Salary             Number(8,2),
  8    City               VARCHAR2(10 BYTE),
  9    Description        VARCHAR2(15 BYTE)
 10  )
 11  /
Table created.
SQL>
SQL> -- prepare data
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2               values ("01","Jason",    "Martin",  to_date("19960725","YYYYMMDD"), to_date("20060725","YYYYMMDD"), 1234.56, "Toronto",  "Programmer")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("02","Alison",   "Mathews", to_date("19760321","YYYYMMDD"), to_date("19860221","YYYYMMDD"), 6661.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("03","James",    "Smith",   to_date("19781212","YYYYMMDD"), to_date("19900315","YYYYMMDD"), 6544.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("04","Celia",    "Rice",    to_date("19821024","YYYYMMDD"), to_date("19990421","YYYYMMDD"), 2344.78, "Vancouver","Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary,  City,       Description)
  2                values("05","Robert",   "Black",   to_date("19840115","YYYYMMDD"), to_date("19980808","YYYYMMDD"), 2334.78, "Vancouver","Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("06","Linda",    "Green",   to_date("19870730","YYYYMMDD"), to_date("19960104","YYYYMMDD"), 4322.78,"New York",  "Tester")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("07","David",    "Larry",   to_date("19901231","YYYYMMDD"), to_date("19980212","YYYYMMDD"), 7897.78,"New York",  "Manager")
  3  /
1 row created.
SQL> insert into Employee(ID,  First_Name, Last_Name, Start_Date,                     End_Date,                       Salary, City,        Description)
  2                values("08","James",    "Cat",     to_date("19960917","YYYYMMDD"), to_date("20020415","YYYYMMDD"), 1232.78,"Vancouver", "Tester")
  3  /
1 row created.
SQL>
SQL>
SQL>
SQL> -- display data in the table
SQL> select * from Employee
  2  /
ID   FIRST_NAME LAST_NAME  START_DAT END_DATE      SALARY CITY       DESCRIPTION
---- ---------- ---------- --------- --------- ---------- ---------- ---------------
01   Jason      Martin     25-JUL-96 25-JUL-06    1234.56 Toronto    Programmer
02   Alison     Mathews    21-MAR-76 21-FEB-86    6661.78 Vancouver  Tester
03   James      Smith      12-DEC-78 15-MAR-90    6544.78 Vancouver  Tester
04   Celia      Rice       24-OCT-82 21-APR-99    2344.78 Vancouver  Manager
05   Robert     Black      15-JAN-84 08-AUG-98    2334.78 Vancouver  Tester
06   Linda      Green      30-JUL-87 04-JAN-96    4322.78 New York   Tester
07   David      Larry      31-DEC-90 12-FEB-98    7897.78 New York   Manager
08   James      Cat        17-SEP-96 15-APR-02    1232.78 Vancouver  Tester
8 rows selected.
SQL>
SQL>
SQL> CREATE VIEW myView AS
  2  SELECT *
  3  FROM employee
  4  WITH READ ONLY CONSTRAINT my_view_read_only;
View created.
SQL>
SQL> INSERT INTO myView (id) VALUES (1);
INSERT INTO myView (id) VALUES (1)
                    *
ERROR at line 1:
ORA-01733: virtual column not allowed here

SQL>
SQL> drop view myView;
View dropped.
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.
SQL>
SQL>


Use view based on user-defind type

SQL> create type addressType as object
  2  (Street  VARCHAR2(50),
  3   City    VARCHAR2(25),
  4   State   CHAR(2),
  5   Zip     NUMBER);
  6  /
SQL> create type personType as object
  2  (Name     VARCHAR2(25),
  3   Address  addressType);
  4  /
SQL>
SQL>
SQL> create table emp
  2  (cid NUMBER   primary key,
  3   Name        VARCHAR2(25),
  4   Street      VARCHAR2(50),
  5   City        VARCHAR2(25),
  6   State       CHAR(2),
  7   Zip         NUMBER);
SQL>
SQL> create view empView (cid, Person) as
  2  select cid,personType(Name,addressType(Street, City, State, Zip))
  3    from emp;
SQL>
SQL> drop view empView;
SQL> drop table emp;
SQL>
SQL> drop type personType;
SQL>
SQL> drop type addressType;
SQL>
SQL>


Views

  1. A view is a predefined query on one or more tables.
  2. Retrieving information from a view is done in the same manner as retrieving from a table.
  3. With some views you can also perform DML operations (delete, insert, update) on the base tables.
  4. Views don"t store data, they only access rows in the base tables.
  5. user_tables, user_sequences, and user_indexes are all views.
  6. View Only allows a user to retrieve data.
  7. view can hide the underlying base tables.
  8. By writing complex queries as a view, we can hide complexity from an end user.
  9. View only allows a user to access certain rows in the base tables.

8. 1. Create View 8. 1. 1. Views 8. 1. 2. <A href="/Tutorial/Oracle/0160__View/CreatingandUsingaView.htm">Creating and Using a View</a> 8. 1. 3. <A href="/Tutorial/Oracle/0160__View/CreatingandUsingSimpleViews.htm">Creating and Using Simple Views</a> 8. 1. 4. <A href="/Tutorial/Oracle/0160__View/Choosespecificcolumnfrombasetable.htm">Choose specific column from base table</a> 8. 1. 5. <A href="/Tutorial/Oracle/0160__View/CreatingaViewwithaCHECKOPTIONConstraint.htm">Creating a View with a CHECK OPTION Constraint</a> 8. 1. 6. <A href="/Tutorial/Oracle/0160__View/CreatingaViewwithaREADONLYConstraint.htm">Creating a View with a READ ONLY Constraint</a> 8. 1. 7. <A href="/Tutorial/Oracle/0160__View/Createviewbasedonuserdefinedfunction.htm">Create view based on user-defined function</a> 8. 1. 8. <A href="/Tutorial/Oracle/0160__View/Createaviewbyjoiningtwotables.htm">Create a view by joining two tables</a> 8. 1. 9. <A href="/Tutorial/Oracle/0160__View/Createviewbasedonaggregatefunction.htm">Create view based on aggregate function</a> 8. 1. 10. <A href="/Tutorial/Oracle/0160__View/auserdefinedtypeview.htm">a user-defined type view</a> 8. 1. 11. <A href="/Tutorial/Oracle/0160__View/CREATEMATERIALIZEDVIEWwithTABLESPACE.htm">CREATE MATERIALIZED VIEW with TABLESPACE</a> 8. 1. 12. <A href="/Tutorial/Oracle/0160__View/CREATEMATERIALIZEDVIEWwithrowid.htm">CREATE MATERIALIZED VIEW with rowid</a> 8. 1. 13. <A href="/Tutorial/Oracle/0160__View/Createviewbyjointhreetables.htm">Create view by join three tables</a> 8. 1. 14. <A href="/Tutorial/Oracle/0160__View/Createviewonsinglefieldofatype.htm">Create view on single field of a type</a> 8. 1. 15. <A href="/Tutorial/Oracle/0160__View/creatematerializedviewempdeptbuildimmediaterefreshondemandenablequeryrewrite.htm">create materialized view emp_dept build immediate refresh on demand enable query rewrite</a> 8. 1. 16. <A href="/Tutorial/Oracle/0160__View/Useviewbasedonuserdefindtype.htm">Use view based on user-defind type</a>