using SELECT DISTINCT or a GROUP BY statement in the inner query : Correlated subquery « Subquery « SQL Server / T-SQL Tutorial

1. SQL Server / T-SQL Tutorial
2. Subquery
3. Correlated subquery

6>
7>
8>
9> CREATE TABLE Product(
10>     ProductID               int                NOT NULL,
11>     Name                    nvarchar(25)       NOT NULL,
12>     ProductNumber           nvarchar(25)               ,
13>     Color                   nvarchar(15)       NULL,
14>     StandardCost            money              NOT NULL,
15>     Size                    nvarchar(5)        NULL,
16>     Weight                  decimal(8, 2)      NULL,
17>     ProductLine             nchar(20)           NULL,
18>     SellStartDate           datetime           NOT NULL,
19>     SellEndDate             datetime           NULL
20> )
21> 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 ID
4>   , Name
5> FROM Product AS P
6> WHERE 1 =
7>   (SELECT DISTINCT ProductID
8>   FROM SalesOrderDetail As SD
9>   WHERE P.ProductID = SD.ProductID)
10> GO
1>
2> drop table Product;
3> GO
1>
2>
3> drop table SalesOrderDetail;
4> GO