SQL Server/T-SQL Tutorial/Query/DISTINCT — различия между версиями
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Версия 13:46, 26 мая 2010
Содержание
- 1 A SELECT statement that eliminates duplicate rows
- 2 A summary query that uses the DISTINCT keyword
- 3 Correlated subquery using Distinct
- 4 DISTINCT can be used only once in a SELECT list, and it must precede all column names in that list.
- 5 Distinct with two columns
- 6 Using SELECT DISTINCT or a GROUP BY statement in the inner query
- 7 When the DISTINCT keyword is used, all duplicate values are eliminated before the function COUNT is applied.
A SELECT statement that eliminates duplicate rows
DISTINCT keyword prevents duplicate (identical) rows from being included in the result set.
It also causes the result set to be sorted by its first column.
To use the DISTINCT keyword, code it immediately after the SELECT keyword.
13>
14>
15> create table Bankers(
16> BankerID Integer,
17> BankerName VARCHAR(20),
18> BankerContactLName VARCHAR(20),
19> BankerContactFName VARCHAR(20),
20> BankerCity VARCHAR(20),
21> BankerState VARCHAR(20),
22> BankerZipCode VARCHAR(20),
23> BankerPhone VARCHAR(20)
24> )
25> GO
1>
2> insert into Bankers values (1, "ABC Inc.","Joe","Smith","Vancouver","BC","11111","111-111-1111");
3> GO
(1 rows affected)
1> insert into Bankers values (2, "DEF Inc.","Red","Rice", "New York", "DE","22222","222-222-2222");
2> GO
(1 rows affected)
1> insert into Bankers values (3, "HJI Inc.","Kit","Cat", "Paris", "CA","33333","333-333-3333");
2> GO
(1 rows affected)
1> insert into Bankers values (4, "QWE Inc.","Git","Black","Regina", "ER","44444","444-444-4444");
2> GO
(1 rows affected)
1> insert into Bankers values (5, "RTY Inc.","Wil","Lee", "Toronto", "YU","55555","555-555-5555");
2> GO
(1 rows affected)
1> insert into Bankers values (6, "YUI Inc.","Ted","Larry","Calgary", "TY","66666","666-666-6666");
2> GO
(1 rows affected)
1> insert into Bankers values (7, "OIP Inc.","Yam","Act", "San Franc","FG","77777","777-777-7777");
2> GO
(1 rows affected)
1> insert into Bankers values (8, "SAD Inc.","Hit","Eat", "Orland", "PO","88888","888-888-8888");
2> GO
(1 rows affected)
1> insert into Bankers values (9, "DFG Inc.","Sad","Lee", "Wisler", "PL","99999","999-999-9999");
2> GO
(1 rows affected)
1> insert into Bankers values (0, "GHJ Inc.","Bit","Lee", "Ticker", "MN","00000","000-000-0000");
2> GO
(1 rows affected)
1>
2>
3> SELECT DISTINCT BankerCity, BankerState
4> FROM Bankers
5> GO
BankerCity BankerState
-------------------- --------------------
Calgary TY
New York DE
Orland PO
Paris CA
Regina ER
San Franc FG
Ticker MN
Toronto YU
Vancouver BC
Wisler PL
(10 rows affected)
1>
2> drop table Bankers;
3> GO
1>
2>
A summary query that uses the DISTINCT keyword
4>
5>
6> create table Billings (
7> BankerID INTEGER,
8> BillingNumber INTEGER,
9> BillingDate datetime,
10> BillingTotal INTEGER,
11> TermsID INTEGER,
12> BillingDueDate datetime ,
13> PaymentTotal INTEGER,
14> CreditTotal INTEGER
15>
16> );
17> GO
1>
2> INSERT INTO Billings VALUES (1, 1, "2005-01-22", 165, 1,"2005-04-22",123,321);
3> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (2, 2, "2001-02-21", 165, 1,"2002-02-22",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (3, 3, "2003-05-02", 165, 1,"2005-04-12",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (4, 4, "1999-03-12", 165, 1,"2005-04-18",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (5, 5, "2000-04-23", 165, 1,"2005-04-17",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (6, 6, "2001-06-14", 165, 1,"2005-04-18",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (7, 7, "2002-07-15", 165, 1,"2005-04-19",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (8, 8, "2003-08-16", 165, 1,"2005-04-20",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (9, 9, "2004-09-17", 165, 1,"2005-04-21",123,321);
2> GO
(1 rows affected)
1> INSERT INTO Billings VALUES (0, 0, "2005-10-18", 165, 1,"2005-04-22",123,321);
2> GO
(1 rows affected)
1>
2>
3> SELECT COUNT(DISTINCT BankerID) AS NumberOfBankers,
4> COUNT(BankerID) AS NumberOfBillings,
5> AVG(BillingTotal) AS AverageBillingAmount,
6> SUM(BillingTotal) AS TotalBillingAmount
7> FROM Billings
8> WHERE BillingDate > "2002-01-01"
9> GO
NumberOfBankers NumberOfBillings AverageBillingAmount TotalBillingAmount
--------------- ---------------- -------------------- ------------------
6 6 165 990
(1 rows affected)
1>
2>
3>
4> drop table Billings;
5> GO
1>
2>
7> CREATE TABLE Product(
8> ProductID int NOT NULL,
9> Name nvarchar(25) NOT NULL,
10> ProductNumber nvarchar(25) ,
11> Color nvarchar(15) NULL,
12> StandardCost money NOT NULL,
13> Size nvarchar(5) NULL,
14> Weight decimal(8, 2) NULL,
15> ProductLine nchar(20) NULL,
16> SellStartDate datetime NOT NULL,
17> SellEndDate datetime NULL
18> )
19> GO
1> insert into Product values(1,"Product A", "1","Red",123.123,"1",1,"ProductLine A","1999-03-22","2000-03-22");
2> GO
(1 rows affected)
1> insert into Product values(2,"Product B", "2","Yellow",234.234,"1",3,"ProductLine B","2000-03-22","2001-03-22");
2> GO
(1 rows affected)
1> insert into Product values(3,"Product C", "3","Pink",345.345,"1",3,"ProductLine V","2001-09-22","2006-02-22");
2> GO
(1 rows affected)
1> insert into Product values(4,"Product D", "4","White",456.456,"1",4,"ProductLine D","2002-08-22","2006-03-22");
2> GO
(1 rows affected)
1> insert into Product values(5,"Product E", "5","Black",567.567,"1",5,"ProductLine E","2003-01-22","2003-04-22");
2> GO
(1 rows affected)
1> insert into Product values(6,"Product F", "6","Blue",678.678,"1",6,"ProductLine W","2004-02-22","2005-05-22");
2> GO
(1 rows affected)
1> insert into Product values(7,"Product G", "7","Drak",789.789,"1",7,"ProductLine Q","2005-03-22","2006-03-22");
2> GO
(1 rows affected)
1> insert into Product values(8,"Product H", "8","Gray",234.123,"1",8,"ProductLine F","2006-04-22","2006-09-22");
2> GO
(1 rows affected)
1> insert into Product values(9,"Product I", "9","Red",543.123,"1",9,"ProductLine R","2007-05-22","2008-03-22");
2> GO
(1 rows affected)
1> insert into Product values(0,"Product J", "0","Gold",765.123,"1",0,"ProductLine J","2008-06-22","2009-03-22");
2> GO
(1 rows affected)
1>
2>
3>
4> CREATE TABLE SalesOrderDetail(
5> SalesOrderID int NOT NULL,
6> SalesOrderDetailID int NOT NULL,
7> CarrierTrackingNumber nvarchar(25) NULL,
8> OrderQty smallint NOT NULL,
9> ProductID int NOT NULL,
10> SpecialOfferID int NOT NULL,
11> UnitPrice money NOT NULL,
12> UnitPriceDiscount money NOT NULL DEFAULT (0.0),
13> LineTotal AS ISNULL([UnitPrice] * (1.0 - [UnitPriceDiscount]) * [OrderQty], 0.0)
14> );
15> GO
1>
2> insert into SalesOrderDetail values (1,1,"1",1,1,1,$1,$1);
3> GO
(1 rows affected)
1> insert into SalesOrderDetail values (2,2,"2",2,2,2,$2,$2);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (3,3,"3",3,3,3,$3,$3);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (4,4,"4",4,4,4,$4,$4);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (5,5,"5",5,5,5,$5,$5);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (6,6,"6",6,6,6,$6,$6);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (7,7,"7",7,7,7,$7,$7);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (8,8,"8",8,8,8,$8,$8);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (9,9,"9",9,9,9,$9,$9);
2> GO
(1 rows affected)
1>
2>
3> SELECT ProductID
4> , Name
5> FROM Product AS P
6> WHERE 1 =
7> (SELECT DISTINCT SpecialOfferID
8> FROM SalesOrderDetail As SD
9> WHERE P.ProductID = SD.ProductID)
10> GO
ProductID Name
----------- -------------------------
1 Product A
(1 rows affected)
1>
2> drop table Product;
3> GO
1>
2>
3> drop table SalesOrderDetail;
4> GO
DISTINCT can be used only once in a SELECT list, and it must precede all column names in that list.
the DISTINCT clause displays all rows where the combination of columns is distinct.
9> CREATE TABLE employee(
10> id INTEGER NOT NULL PRIMARY KEY,
11> first_name VARCHAR(10),
12> last_name VARCHAR(10),
13> salary DECIMAL(10,2),
14> start_Date DATETIME,
15> region VARCHAR(10),
16> city VARCHAR(20),
17> managerid INTEGER
18> );
19> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver",3);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown",4);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris",5);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London",6);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton",7);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary",8);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto",10);
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id first_name last_name salary start_Date region city managerid
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------
1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver 3
2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown 4
3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris 5
4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London 6
5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton 7
6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary 8
7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York 9
8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina 9
9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto 10
(9 rows affected)
1>
2> select distinct region from employee;
3> GO
region
----------
East
North
South
West
(4 rows affected)
1>
2>
3> drop table employee;
4> GO
1>
Distinct with two columns
3> IF OBJECT_ID("dbo.Sessions") IS NOT NULL
4> DROP TABLE dbo.Sessions;
5> GO
1>
2> CREATE TABLE dbo.Sessions
3> (
4> keycol INT NOT NULL IDENTITY PRIMARY KEY,
5> app VARCHAR(10) NOT NULL,
6> usr VARCHAR(10) NOT NULL,
7> starttime DATETIME NOT NULL,
8> endtime DATETIME NOT NULL,
9> CHECK(endtime > starttime)
10> );
11> GO
1>
2> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user1", "20060212 08:30", "20060212 10:30");
3> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user2", "20060212 08:30", "20060212 08:45");
4> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user1", "20060212 09:00", "20060212 09:30");
5> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user2", "20060212 09:15", "20060212 10:30");
6> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user1", "20060212 09:15", "20060212 09:30");
7> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user2", "20060212 10:30", "20060212 14:30");
8> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user1", "20060212 10:45", "20060212 11:30");
9> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app1", "user2", "20060212 11:00", "20060212 12:30");
10> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user1", "20060212 08:30", "20060212 08:45");
11> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user2", "20060212 09:00", "20060212 09:30");
12> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user1", "20060212 11:45", "20060212 12:00");
13> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user2", "20060212 12:30", "20060212 14:00");
14> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user1", "20060212 12:45", "20060212 13:30");
15> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user2", "20060212 13:00", "20060212 14:00");
16> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user1", "20060212 14:00", "20060212 16:30");
17> INSERT INTO dbo.Sessions(app, usr, starttime, endtime) VALUES("app2", "user2", "20060212 15:30", "20060212 17:00");
18> GO
1>
2> SELECT DISTINCT app, starttime AS ts
3> FROM dbo.Sessions;
4> GO
app ts
---------- -----------------------
app1 2006-02-12 08:30:00.000
app1 2006-02-12 09:00:00.000
app1 2006-02-12 09:15:00.000
app1 2006-02-12 10:30:00.000
app1 2006-02-12 10:45:00.000
app1 2006-02-12 11:00:00.000
app2 2006-02-12 08:30:00.000
app2 2006-02-12 09:00:00.000
app2 2006-02-12 11:45:00.000
app2 2006-02-12 12:30:00.000
app2 2006-02-12 12:45:00.000
app2 2006-02-12 13:00:00.000
app2 2006-02-12 14:00:00.000
app2 2006-02-12 15:30:00.000
1>
2> drop table sessions;
3> GO
1>
Using SELECT DISTINCT or a GROUP BY statement in the inner query
7> CREATE TABLE Product(
8> ProductID int NOT NULL,
9> Name nvarchar(25) NOT NULL,
10> ProductNumber nvarchar(25) ,
11> Color nvarchar(15) NULL,
12> StandardCost money NOT NULL,
13> Size nvarchar(5) NULL,
14> Weight decimal(8, 2) NULL,
15> ProductLine nchar(20) NULL,
16> SellStartDate datetime NOT NULL,
17> SellEndDate datetime NULL
18> )
19> GO
1> insert into Product values(1,"Product A", "1","Red",123.123,"1",1,"ProductLine A","1999-03-22","2000-03-22");
2> GO
(1 rows affected)
1> insert into Product values(2,"Product B", "2","Yellow",234.234,"1",3,"ProductLine B","2000-03-22","2001-03-22");
2> GO
(1 rows affected)
1> insert into Product values(3,"Product C", "3","Pink",345.345,"1",3,"ProductLine V","2001-09-22","2006-02-22");
2> GO
(1 rows affected)
1> insert into Product values(4,"Product D", "4","White",456.456,"1",4,"ProductLine D","2002-08-22","2006-03-22");
2> GO
(1 rows affected)
1> insert into Product values(5,"Product E", "5","Black",567.567,"1",5,"ProductLine E","2003-01-22","2003-04-22");
2> GO
(1 rows affected)
1> insert into Product values(6,"Product F", "6","Blue",678.678,"1",6,"ProductLine W","2004-02-22","2005-05-22");
2> GO
(1 rows affected)
1> insert into Product values(7,"Product G", "7","Drak",789.789,"1",7,"ProductLine Q","2005-03-22","2006-03-22");
2> GO
(1 rows affected)
1> insert into Product values(8,"Product H", "8","Gray",234.123,"1",8,"ProductLine F","2006-04-22","2006-09-22");
2> GO
(1 rows affected)
1> insert into Product values(9,"Product I", "9","Red",543.123,"1",9,"ProductLine R","2007-05-22","2008-03-22");
2> GO
(1 rows affected)
1> insert into Product values(0,"Product J", "0","Gold",765.123,"1",0,"ProductLine J","2008-06-22","2009-03-22");
2> GO
(1 rows affected)
1>
2>
3>
4> CREATE TABLE SalesOrderDetail(
5> SalesOrderID int NOT NULL,
6> SalesOrderDetailID int NOT NULL,
7> CarrierTrackingNumber nvarchar(25) NULL,
8> OrderQty smallint NOT NULL,
9> ProductID int NOT NULL,
10> SpecialOfferID int NOT NULL,
11> UnitPrice money NOT NULL,
12> UnitPriceDiscount money NOT NULL DEFAULT (0.0),
13> LineTotal AS ISNULL([UnitPrice] * (1.0 - [UnitPriceDiscount]) * [OrderQty], 0.0)
14> );
15> GO
1>
2> insert into SalesOrderDetail values (1,1,"1",1,1,1,$1,$1);
3> GO
(1 rows affected)
1> insert into SalesOrderDetail values (2,2,"2",2,2,2,$2,$2);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (3,3,"3",3,3,3,$3,$3);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (4,4,"4",4,4,4,$4,$4);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (5,5,"5",5,5,5,$5,$5);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (6,6,"6",6,6,6,$6,$6);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (7,7,"7",7,7,7,$7,$7);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (8,8,"8",8,8,8,$8,$8);
2> GO
(1 rows affected)
1> insert into SalesOrderDetail values (9,9,"9",9,9,9,$9,$9);
2> GO
(1 rows affected)
1>
2>
3> SELECT ProductID
4> , Name
5> FROM Product AS P
6> WHERE 1 =
7> (SELECT DISTINCT SpecialOfferID
8> FROM SalesOrderDetail As SD
9> WHERE P.ProductID = SD.ProductID)
10> GO
ProductID Name
----------- -------------------------
1 Product A
(1 rows affected)
1>
2> drop table Product;
3> GO
1>
2>
3> drop table SalesOrderDetail;
4> GO
When the DISTINCT keyword is used, all duplicate values are eliminated before the function COUNT is applied.
This form of COUNT does not count rows with null values for the column.
4>
5>
6> CREATE TABLE employee(
7> id INTEGER NOT NULL PRIMARY KEY,
8> first_name VARCHAR(10),
9> last_name VARCHAR(10),
10> salary DECIMAL(10,2),
11> start_Date DATETIME,
12> region VARCHAR(10),
13> city VARCHAR(20),
14> managerid INTEGER
15> );
16> GO
1> INSERT INTO employee VALUES (1, "Jason" , "Martin", 5890,"2005-03-22","North","Vancouver",3);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (2, "Alison", "Mathews",4789,"2003-07-21","South","Utown",4);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (3, "James" , "Smith", 6678,"2001-12-01","North","Paris",5);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (4, "Celia" , "Rice", 5567,"2006-03-03","South","London",6);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (5, "Robert", "Black", 4467,"2004-07-02","East","Newton",7);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (6, "Linda" , "Green" , 6456,"2002-05-19","East","Calgary",8);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (7, "David" , "Larry", 5345,"2008-03-18","West","New York",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (8, "James" , "Cat", 4234,"2007-07-17","West","Regina",9);
2> GO
(1 rows affected)
1> INSERT INTO employee VALUES (9, "Joan" , "Act", 6123,"2001-04-16","North","Toronto",10);
2> GO
(1 rows affected)
1>
2> select * from employee;
3> GO
id first_name last_name salary start_Date region city managerid
----------- ---------- ---------- ------------ ----------------------- ---------- -------------------- -----------
1 Jason Martin 5890.00 2005-03-22 00:00:00.000 North Vancouver 3
2 Alison Mathews 4789.00 2003-07-21 00:00:00.000 South Utown 4
3 James Smith 6678.00 2001-12-01 00:00:00.000 North Paris 5
4 Celia Rice 5567.00 2006-03-03 00:00:00.000 South London 6
5 Robert Black 4467.00 2004-07-02 00:00:00.000 East Newton 7
6 Linda Green 6456.00 2002-05-19 00:00:00.000 East Calgary 8
7 David Larry 5345.00 2008-03-18 00:00:00.000 West New York 9
8 James Cat 4234.00 2007-07-17 00:00:00.000 West Regina 9
9 Joan Act 6123.00 2001-04-16 00:00:00.000 North Toronto 10
(9 rows affected)
1>
2> SELECT region, COUNT(DISTINCT region) job_count
3> FROM employee
4> GROUP BY region
5> GO
region job_count
---------- -----------
East 1
North 1
South 1
West 1
(4 rows affected)
1> drop table employee;
2> GO