An one-to-many relation : One to many « Table Join « SQL Server / T-SQL Tutorial

1. SQL Server / T-SQL Tutorial
2. Table Join
3. One to many

3> CREATE TABLE Classes(
4>     ClassID int PRIMARY KEY,
5>     ClassTitle varchar(50)
6> )
7> GO
1>
2> CREATE TABLE ClassGrades(
3>     ClassID int REFERENCES Classes(ClassID)
4>         ON UPDATE CASCADE,
5>     StudentID int,
6>     GradeLetter varchar(2),
7>     Constraint PK_ClassGrades
8>         PRIMARY KEY(ClassID, StudentID)
9> )
10>
11> INSERT Classes VALUES(1,'SQL')
12> INSERT Classes VALUES(999,'Java')
13> GO

(1 rows affected)

(1 rows affected)
1>
2> INSERT ClassGrades VALUES(1, 1, 'C+')
3>
4> INSERT ClassGrades VALUES(1, 2, 'A+')
5> INSERT ClassGrades VALUES(999, 2, 'A')
6> GO

(1 rows affected)

(1 rows affected)

(1 rows affected)
1>
2>
3> SELECT CG.StudentID, C.ClassTitle, CG.GradeLetter
4> FROM Classes C, ClassGrades CG
5> WHERE C.ClassID = CG.ClassID
6> GO
StudentID   ClassTitle                                         GradeLetter
----------- -------------------------------------------------- -----------
          1 SQL                                                C+
          2 SQL                                                A+
          2 Java                                               A

(3 rows affected)
1>
2> UPDATE Classes
3> SET ClassTitle = 'The Life of Jesus Christ'
4> WHERE ClassID = 999
5> GO

(1 rows affected)
1>
2> SELECT CG.StudentID, C.ClassTitle, CG.GradeLetter
3> FROM Classes C, ClassGrades CG
4> WHERE C.ClassID = CG.ClassID
5> GO
StudentID   ClassTitle                                         GradeLetter
----------- -------------------------------------------------- -----------
          1 SQL                                                C+
          2 SQL                                                A+
          2 The Life of Jesus Christ                           A

(3 rows affected)
1>
2>
3> drop table ClassGrades;
4> GO
1>
2> drop table Classes;
3> GO