SQL Server/T-SQL/Select Query/Group BY — различия между версиями

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Текущая версия на 10:21, 26 мая 2010

Combine MAX function with group by

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> SELECT City, MIN(Salary),MAX(Salary)
3> FROM Employee
4> WHERE ID BETWEEN 1 AND 10
5> GROUP BY City
6> GO
City
---------- ----------- -----------
New York         40420       90620
Toronto          24020       70060
Vancouver        14420       80026
(3 rows affected)
1>
2>
3>
4>
5>
6> drop table employee
7> GO
1>



Combine MIN function with group by

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> SELECT City, MIN(Salary),MAX(Salary)
3> FROM Employee
4> WHERE ID BETWEEN 1 AND 10
5> GROUP BY City
6> GO
City
---------- ----------- -----------
New York         40420       90620
Toronto          24020       70060
Vancouver        14420       80026
(3 rows affected)
1>
2>
3>
4>
5>
6> drop table employee
7> GO
1>



Count() and Sum() with group by and column alias

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> SELECT  City
3>       , SUM(Salary) As QtySum
4>       , COUNT(salary) As DetailCount
5> FROM Employee
6> GROUP BY City
7> GO
City       QtySum      DetailCount
---------- ----------- -----------
New York        171660           3
Toronto         154100           3
Vancouver       120466           3
(3 rows affected)
1>
2> drop table employee
3> GO
1>



Count with "group by"

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> SELECT City, COUNT(*) "Employees"
3> FROM Employee
4> GROUP BY City
5> GO
City       Employees
---------- -----------
New York             3
Toronto              3
Vancouver            3
(3 rows affected)
1>
2>
3> drop table employee
4> GO
1>



GROUP BY builds different groups for all possible values (NULL, too!)

1>
2> CREATE TABLE works_on        (emp_no       INTEGER NOT NULL,
3>                         project_no    CHAR(4) NOT NULL,
4>                         job CHAR (15) NULL,
5>                         enter_date    DATETIME NULL)
6>
7> insert into works_on values (1, "p1", "analyst", "1997.10.1")
8> insert into works_on values (1, "p3", "manager", "1999.1.1")
9> insert into works_on values (2, "p2", "clerk",   "1998.2.15")
10> insert into works_on values (2, "p2",  NULL,     "1998.6.1")
11> insert into works_on values (3, "p2",  NULL,     "1997.12.15")
12> insert into works_on values (4, "p3", "analyst", "1998.10.15")
13> insert into works_on values (5, "p1", "manager", "1998.4.15")
14> insert into works_on values (6, "p1",  NULL,     "1998.8.1")
15> insert into works_on values (7, "p2", "clerk",   "1999.2.1")
16> insert into works_on values (8, "p3", "clerk",   "1997.11.15")
17> insert into works_on values (7, "p1", "clerk",   "1998.1.4")
18> GO
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
(1 rows affected)
1>
2> -- GROUP BY builds different groups for all possible values (NULL, too!)
3>
4> SELECT project_no, job FROM works_on GROUP BY project_no, job
5> GO
project_no job
---------- ---------------
p1         NULL
p1         analyst
p1         clerk
p1         manager
p2         NULL
p2         clerk
p3         analyst
p3         clerk
p3         manager
(9 rows affected)
1>
2> drop table works_on
3> GO
1>



GROUP BY clause with an aggregator "SUM()"

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> --GROUP BY clause with an aggregator "SUM()".
3>
4> SELECT region, SUM(Salary)
5> FROM Employee
6> WHERE ID BETWEEN 1 AND 10
7> GROUP BY Region
8> GO
region
------ -----------
N           151120
W           295106
(2 rows affected)
1>
2>
3> drop table employee
4> GO
1>



Simple "group by" demo

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> SELECT Name
3> FROM Employee
4> GROUP BY Name
5> GO
Name
----------
Alison
Celia
Chris
David
James
Jason
Linda
Mary
Robert
(9 rows affected)
1>
2> drop table employee
3> GO
1>



Subquery as one column

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> create table job(
3>     ID              int,
4>     title nvarchar  (10),
5>     averageSalary   int)
6> GO
1>
2>
3>
4> insert into job(ID, title, averageSalary) values(1,"Developer",3000)
5> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(2,"Tester", 4000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(3,"Designer", 5000)
2> GO
(1 rows affected)
1> insert into job(ID, title, averageSalary) values(4,"Programmer", 6000)
2> GO
(1 rows affected)
1>
2> select * from job
3> GO
ID          title      averageSalary
----------- ---------- -------------
          1 Developer           3000
          2 Tester              4000
          3 Designer            5000
          4 Programmer          6000
(4 rows affected)
1>
2> SELECT ID
3>        , (SELECT Title FROM job
4>           WHERE Employee.ID = Job.ID)
5>             AS Title
6> FROM Employee
7> GO
ID          Title
----------- ----------
          1 Developer
          2 Tester
          3 Designer
          4 Programmer
          5 NULL
          6 NULL
          7 NULL
          8 NULL
          9 NULL
(9 rows affected)
1>
2> drop table employee
3> GO



When grouping on more than one column, every unique combination of grouped values produces a row in the result set

1> create table employee(
2>     ID          int,
3>     name        nvarchar (10),
4>     salary      int,
5>     start_date  datetime,
6>     city        nvarchar (10),
7>     region      char (1))
8> GO
1>
2> insert into employee (ID, name,    salary, start_date, city,       region)
3>               values (1,  "Jason", 40420,  "02/01/94", "New York", "W")
4> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (2,  "Robert",14420,  "01/02/95", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (3,  "Celia", 24020,  "12/03/96", "Toronto",  "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (4,  "Linda", 40620,  "11/04/97", "New York", "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (5,  "David", 80026,  "10/05/98", "Vancouver","W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (6,  "James", 70060,  "09/06/99", "Toronto",  "N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (7,  "Alison",90620,  "08/07/00", "New York", "W")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (8,  "Chris", 26020,  "07/08/01", "Vancouver","N")
3> GO
(1 rows affected)
1> insert into employee (ID, name,    salary, start_date, city,       region)
2>               values (9,  "Mary",  60020,  "06/09/02", "Toronto",  "W")
3> GO
(1 rows affected)
1>
2> select * from employee
3> GO
ID          name       salary      start_date              city       region
----------- ---------- ----------- ----------------------- ---------- ------
          1 Jason            40420 1994-02-01 00:00:00.000 New York   W
          2 Robert           14420 1995-01-02 00:00:00.000 Vancouver  N
          3 Celia            24020 1996-12-03 00:00:00.000 Toronto    W
          4 Linda            40620 1997-11-04 00:00:00.000 New York   N
          5 David            80026 1998-10-05 00:00:00.000 Vancouver  W
          6 James            70060 1999-09-06 00:00:00.000 Toronto    N
          7 Alison           90620 2000-08-07 00:00:00.000 New York   W
          8 Chris            26020 2001-07-08 00:00:00.000 Vancouver  N
          9 Mary             60020 2002-06-09 00:00:00.000 Toronto    W
(9 rows affected)
1>
2> -- When grouping on more than one column, every unique combination of grouped values produces a row in the result set.
3>
4> SELECT City
5>       , Region
6> FROM Employee
7> GROUP BY City, Region
8> ORDER BY City, Region
9> GO
City       Region
---------- ------
New York   N
New York   W
Toronto    N
Toronto    W
Vancouver  N
Vancouver  W
(6 rows affected)
1>
2>
3> drop table employee
4> GO
1>