Oracle PL/SQL Tutorial/Query Select/Columns — различия между версиями

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Текущая версия на 10:11, 26 мая 2010

Combined columns and renaming

SQL> create table emp(
  2           emp_id                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          ,company_name           varchar2(50));
Table created.
SQL>
SQL>
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (1,"Jones","Joe","J","1 Ave","New York","NY","11202","1111","212", "221-4333","Big Company");
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (2,"Smith","Sue","J","1 Street","New York","NY","11444","1111","212", "436-6773","Little Company");
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (3,"X","Peggy","J","1 Drive","New York","NY","45502","2222","212", "234-4444","Medium Company");
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (4,"Murdy","Jill", null,"930 Eady St","New York","NY","45452","6458","212", "634-7733","Wilton Company");
1 row created.
SQL> insert into emp(emp_id,lastname,firstname,midinit,street,city,state,zip,shortZipCode,area_code,phone,company_name)values
  2                      (5,"Oper","Carl","L","19 Studio Drive","New York","NY","67672","3234","212", "243-4243","Wesson and Smith Company");
1 row created.
SQL>
SQL>
SQL> select emp_id,
  2   firstname || " " || lastname as "Name",
  3   city, state
  4    from emp
  5   where state = "RI";
no rows selected
SQL>
SQL> drop table emp;
Table dropped.


Count(*) and column renaming

SQL>
SQL>
SQL> create table product(
  2          product_id          integer     primary key
  3          ,price                  number(7,2)
  4          ,description            varchar2(75)
  5          ,onhand                 number(5,0)
  6          ,reorder                number(5,0)
  7          ,supplier_no            integer
  8  );
Table created.
SQL> -- product Table Inserts:
SQL> insert into product(product_id, price, description, onhand, reorder)values (1,2.50,"Happy Birthday",100,20);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (2,23.00,"Happy Birthday",null,null);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (3,null,"Happy New Year",null,null);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (4,1.50,"Happy New Year",50,10);
1 row created.
SQL>
SQL> select count(*) "No. of Products" from product;
No. of Products
---------------
              4
1 row selected.
SQL>
SQL>
SQL> drop table product;
Table dropped.


DISTINCT tableName.*

SQL>
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> create table offerings
  2  ( course     VARCHAR2(6)
  3  , begindate  DATE
  4  , trainer    NUMBER(4)
  5  , location   VARCHAR2(8)
  6  ) ;
Table created.
SQL> insert into offerings values ("SQL",date "2009-04-12",13,"DALLAS" );
1 row created.
SQL> insert into offerings values ("OAU",date "2009-08-10",4,"CHICAGO");
1 row created.
SQL> insert into offerings values ("SQL",date "2009-10-04",1,"SEATTLE");
1 row created.
SQL> insert into offerings values ("SQL",date "2009-12-13",1,"DALLAS" );
1 row created.
SQL> insert into offerings values ("JAV",date "2009-12-13",4,"SEATTLE");
1 row created.
SQL> insert into offerings values ("XML",date "2000-02-03",1,"DALLAS" );
1 row created.
SQL> insert into offerings values ("JAV",date "2000-02-01",11,"DALLAS" );
1 row created.
SQL> insert into offerings values ("PLS",date "2000-09-11",8,"DALLAS" );
1 row created.
SQL> insert into offerings values ("XML",date "2000-09-18",NULL,"SEATTLE");
1 row created.
SQL> insert into offerings values ("OAU",date "2000-09-27",13,"DALLAS" );
1 row created.
SQL> insert into offerings values ("ERM",date "2001-01-15",NULL, NULL    );
1 row created.
SQL> insert into offerings values ("PRO",date "2001-02-19",NULL,"DALLAS" );
1 row created.
SQL> insert into offerings values ("RSD",date "2001-02-24",8,"CHICAGO");
1 row created.
SQL>
SQL> select DISTINCT e.*
  2  from   emp e
  3         join
  4         offerings o
  5         on e.empno = o.trainer
  6  where  o.course = "SQL";
     EMPNO ENAME    INIT  JOB             MGR BDATE             SAL       COMM
---------- -------- ----- -------- ---------- ---------- ---------- ----------
    DEPTNO
----------
         1 Tom      N     TRAINER          13 17-12-1965        800
        20
        13 Fake     MG                      4 13-02-1959       3000
        20

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


Expression and column renaming

SQL>
SQL>
SQL> create table gift(
  2           gift_id                integer         primary key
  3          ,emp_id                integer
  4          ,register_date              date not null
  5          ,total_price        number(7,2)
  6          ,deliver_date           date
  7          ,deliver_time           varchar2(7)
  8          ,payment        varchar2(2)
  9          ,emp_no                 number(3,0)
 10          ,deliver_name           varchar2(35)
 11          ,message        varchar2(100)
 12  );
Table created.
SQL>
SQL> insert into gift(gift_id,emp_id,register_date,total_price,deliver_date,deliver_time,payment,emp_no,deliver_name,message)values
  2                 (1,1,"14-Feb-1999", 123.12, "14-Feb-1999", "12 noon", "CA",1, null, "Happy Birthday to you");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time ,payment ,emp_no,deliver_name ,message)values
  2                 (2,1,"14-Feb-1999", 50.98, "14-feb-1999", "1 pm", "CA",7, "name1", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values
  2                 (3, 2,"14-Feb-1999", 35.99, "14-feb-1999", "1 pm", "VS",2, "Tom", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values
  2                 (4, 2,"14-Feb-1999", 19.95, "14-feb-1999", "5 pm", "CA",2, "Mary", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message)values
  2                 (5, 6,"4-mar-1999", 10.95, "5-mar-1999", "4:30 pm", "VS", 2, "Jack", "Happy Birthday");
1 row created.
SQL>
SQL> select gift_id, total_price,total_price * 1.1 "Increased Price" from gift;
   GIFT_ID TOTAL_PRICE Increased Price
---------- ----------- ---------------
         1      123.12         135.432
         2       50.98          56.078
         3       35.99          39.589
         4       19.95          21.945
         5       10.95          12.045
5 rows selected.
SQL>
SQL> drop table gift;
Table dropped.


Format date value and column renaming

SQL> create table gift(
  2           gift_id                integer         primary key
  3          ,emp_id                integer
  4          ,register_date              date not null
  5          ,total_price        number(7,2)
  6          ,deliver_date           date
  7          ,deliver_time           varchar2(7)
  8          ,payment        varchar2(2)
  9          ,emp_no                 number(3,0)
 10          ,deliver_name           varchar2(35)
 11          ,message        varchar2(100)
 12  );
Table created.
SQL>
SQL> insert into gift(gift_id,emp_id,register_date,total_price,deliver_date,deliver_time,payment,emp_no,deliver_name,message)values
  2                 (1,1,"14-Feb-1999", 123.12, "14-Feb-1999", "12 noon", "CA",1, null, "Happy Birthday to you");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time ,payment ,emp_no,deliver_name ,message)values
  2                 (2,1,"14-Feb-1999", 50.98, "14-feb-1999", "1 pm", "CA",7, "name1", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values
  2                 (3, 2,"14-Feb-1999", 35.99, "14-feb-1999", "1 pm", "VS",2, "Tom", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message )values
  2                 (4, 2,"14-Feb-1999", 19.95, "14-feb-1999", "5 pm", "CA",2, "Mary", "Happy Birthday");
1 row created.
SQL> insert into gift(gift_id  ,emp_id ,register_date ,total_price ,deliver_date ,deliver_time,payment ,emp_no,deliver_name ,message)values
  2                 (5, 6,"4-mar-1999", 10.95, "5-mar-1999", "4:30 pm", "VS", 2, "Jack", "Happy Birthday");
1 row created.
SQL>
SQL>
SQL> select gift_id, to_char(register_date, "hh24:mi:ss")
  2         as "Order Time"
  3    from gift;
   GIFT_ID Order Ti
---------- --------
         1 00:00:00
         2 00:00:00
         3 00:00:00
         4 00:00:00
         5 00:00:00
5 rows selected.
SQL>
SQL>
SQL> drop table gift;
Table dropped.


Reference one column more than once

SQL> create table product(
  2          product_id          integer     primary key
  3          ,price                  number(7,2)
  4          ,description            varchar2(75)
  5          ,onhand                 number(5,0)
  6          ,reorder                number(5,0)
  7          ,supplier_no            integer
  8  );
Table created.
SQL> -- product Table Inserts:
SQL> insert into product(product_id, price, description, onhand, reorder)values (1,2.50,"Happy Birthday",100,20);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (2,23.00,"Happy Birthday",null,null);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (3,null,"Happy New Year",null,null);
1 row created.
SQL> insert into product(product_id, price, description, onhand, reorder)values (4,1.50,"Happy New Year",50,10);
1 row created.
SQL>
SQL>
SQL> select description, price, price * .068 as tax,
  2         price * 1.068 as "Total"
  3    from product;
DESCRIPTION
---------------------------------------------------------------------------
     PRICE        TAX      Total
---------- ---------- ----------
Happy Birthday
       2.5        .17       2.67
Happy Birthday
        23      1.564     24.564
Happy New Year

Happy New Year
       1.5       .102      1.602

4 rows selected.
SQL>
SQL> drop table product;
Table dropped.


Reference renamed column in order by

SQL>
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",   "Coder", 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", "Coder", 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",  "Coder", 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",   "Coder", 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> select ename, 12*sal+comm yearsal
  2  from   emp
  3  where  job = "Tester"
  4  order  by yearsal desc;
ENAME       YEARSAL
-------- ----------
Jack          19500
Take          18000
Mary          16400
Wil           15500
SQL>
SQL>
SQL> drop table emp;
Table dropped.


Rename case when column

SQL>
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",  "Coder", 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>
SQL> select ename, job
  2  ,      case when job   = "Coder" then "  10%"
  3              when job   = "Designer" then "  20%"
  4              when ename = "Tom"   then "  30%"
  5                                     else "   0%"
  6         end  as raise
  7  from   emp
  8  order  by raise desc, ename;
ENAME    JOB      RAISE
-------- -------- -----
Black    Designer   20%
Jane     Designer   20%
Tom      Coder      10%
Jack     Tester      0%
Mary     Tester      0%
Wil      Tester      0%
6 rows selected.
SQL>
SQL>
SQL> drop table emp;
Table dropped.


Returning Multiple Columns

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)
  8  );
Table created.
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>
SQL> SELECT StudentID, ExamID, Comments FROM SAT;
 STUDENTID     EXAMID
---------- ----------
COMMENTS
--------------------------------------------------------------------------------
         1          1
Satisfactory
         1          2
Good result
         2          3
Hard
         2          5
Simple
         2          6

5 rows selected.
SQL>
SQL>
SQL> drop table SAT;
Table dropped.


Selecting All Columns from a Table with asterisk character (*)

You can use the asterisk character (*) in your select list. The asterisk is used with SELECT to retrieve all columns.



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>
SQL>
SQL> -- clean the table
SQL> drop table Employee
  2  /
Table dropped.


Table renaming in from clause

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",   "Coder", 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", "Coder", 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",  "Coder", 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",   "Coder", 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> select e.ename, e.init, e.job
  2  from   emp e
  3  where  e.deptno = 20;
ENAME    INIT  JOB
-------- ----- --------
Tom      N     Coder
Jane     JM    Designer
Smart    SCJ   Coder
Ana      AA    Coder
Fake     MG    Coder
SQL>
SQL> drop table emp;
Table dropped.


Use table name to reference column name

SQL>
SQL> CREATE TABLE emp (
  2    emp_id               NUMBER,
  3    ename             VARCHAR2(40),
  4    hire_date        DATE DEFAULT sysdate,
  5    end_date DATE,
  6    rate     NUMBER(5,2),
  7    CONSTRAINT emp_pk    PRIMARY KEY (emp_id)
  8  );
Table created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (101, "Mary", to_date("15-Nov-1961","dd-mon-yyyy"),null,169);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (102, "Tom", to_date("16-Sep-1964","dd-mon-yyyy"),to_date("5-May-2004","dd-mon-yyyy"),135);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (104, "Peter", to_date("29-Dec-1987","dd-mon-yyyy"),to_date("1-Apr-2004","dd-mon-yyyy"),99);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (105, "Mike", to_date("15-Jun-2004","dd-mon-yyyy"),null,121);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (107, "Less", to_date("2-Jan-2004","dd-mon-yyyy"),null,45);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (108, "Park", to_date("1-Mar-1994","dd-mon-yyyy"),to_date("15-Nov-2004","dd-mon-yyyy"),220);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (110, "Ink", to_date("4-Apr-2004","dd-mon-yyyy"),to_date("30-Sep-2004","dd-mon-yyyy"),84);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (111, "Tike", to_date("23-Aug-1976","dd-mon-yyyy"),null,100);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (112, "Inn", to_date("15-Nov-1961","dd-mon-yyyy"),to_date("4-Apr-2004","dd-mon-yyyy"),70);
1 row created.
SQL> INSERT INTO emp(emp_id, ename, hire_date,end_date, rate)VALUES (113, "Kate", to_date("3-Mar-2004","dd-mon-yyyy"),to_date("31-Oct-2004","dd-mon-yyyy"),300);
1 row created.
SQL>
SQL> SET ECHO ON
SQL> SELECT emp.emp_id, emp.ename
  2  FROM emp;
       101 Mary
       102 Tom
       104 Peter
       105 Mike
       107 Less
       108 Park
       110 Ink
       111 Tike
       112 Inn
       113 Kate
10 rows selected.
SQL>
SQL>
SQL> drop table emp;
Table dropped.