Group joined tables : GROUP BY « Select Query « Oracle PL / SQL






  1. Oracle PL / SQL
  2. Select Query
  3. GROUP BY

Group joined tables

   
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> create table registrations
  2  ( attendee    NUMBER(4)
  3  , course      VARCHAR2(6)
  4  , begindate   DATE
  5  , evaluation  NUMBER(1)
  6  , constraint  R_PK        primary key(attendee,course,begindate)
  7  ) ;

Table created.

SQL>
SQL> insert into registrations values (2,'SQL',date '2009-04-12',4   );

1 row created.

SQL> insert into registrations values (14,'SQL',date '2009-04-12',5   );

1 row created.

SQL> insert into registrations values (6,'SQL',date '2009-04-12',4   );

1 row created.

SQL> insert into registrations values (11,'SQL',date '2009-04-12',2   );

1 row created.

SQL> insert into registrations values (8,'SQL',date '2009-10-04',NULL);

1 row created.

SQL> insert into registrations values (9,'SQL',date '2009-10-04',3   );

1 row created.

SQL> insert into registrations values (13,'SQL',date '2009-10-04',4   );

1 row created.

SQL> insert into registrations values (13,'SQL',date '2009-12-13',NULL);

1 row created.

SQL> insert into registrations values (12,'XML',date '2000-02-03',4   );

1 row created.

SQL> insert into registrations values (2,'XML',date '2000-02-03',5   );

1 row created.

SQL> insert into registrations values (4,'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 (11,'PLS',date '2000-09-11',NULL);

1 row created.

SQL>
SQL>
SQL> select o.trainer, avg(r.evaluation)
  2  from   offerings o
  3         join
  4         registrations r
  5         using (course,begindate)
  6  group  by o.trainer;

   TRAINER AVG(R.EVALUATION)
---------- -----------------
         1                 4
         8
        13              3.75

SQL>
SQL> drop table registrations;

Table dropped.

SQL>
SQL> drop table offerings;

Table dropped.








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