期末第9章_数据库应用系统开发.ppt
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数据库技术与应用;数据库应用程序开发技术;应用系统的多层结构;数据库设计 ;数据库设计实例;性别;完整性控制;SQL中的CREATE TABLE命令;例: 在学生选课数据库中，定义关系模式SC(snum,cnum,score) 。
CREATE TABLE SC(
snum char(10) NOT NULL FOREIGN KEY (snum) REFERENCES student(snum) ON DELETE CASCADE,
cnum char(10) NOT NULL FOREIGN KEY REFERENCES course ON DELETE CASCADE,
score INT NULL CHECK(score=0 AND score=100),
PRIMARY KEY（snum,cnum）)；;域完整性控制实例;触发器实现完整性控制;CREATE TRIGGER student_delete
ON student
FOR DELETE
AS
DECLARE @_snum AS CHAR(10)
SELECT @_snum=d.snum FROM deleted d
IF NOT EXISTS (SELECT * FROM sc WHERE
snum=@_snum)
BEGIN
PRINT 已删除没有选课的学生！
COMMIT TRAN
END
ELSE
BEGIN
DELETE FROM sc WHERE snum=@_snum
PRINT 成功删除！
END;数据库的实施;数据访问层的设计;ADO.NET DataSet ;.NET Framework 数据提供程序 ;Connection对象 ;应用实例;Private Sub Form1_Load(……) Handles MyBase.Load
Dim sql As String = select * from sc
Dim myconn As New SqlConnection(Initial Catalog=学生选课;Data_
Source=NAONAO;Integrated Security=SSPI;)
Dim adapter As SqlDataAdapter = New SqlDataAdapter(sql, myconn)
Dim sc_dataset As New Data.DataSet
adapter.Fill(sc_dataset, sc)
Dim i As Integer = 0
Dim sum As Integer = 0
For i = 0 To sc_dataset.Tables(sc).Rows.Count – 1
sum = sum + sc_dataset.Tables(sc).Rows(i).Item(score)
Next
sum = sum / i
MsgBox(平均成绩= sum)
End Sub
;Private Sub Form1_Load(……) Handles MyBase.Load
Dim sql As String = select * from sc
Dim myconn As New SqlConnection(Initial Catalog=学生选课;Data_
Source=NAONAO;Integrated Security=SSPI;)
Dim mycmd As New SqlCommand(sql, myconn)
Dim reader_sc As SqlDataReader
Dim i As Integer = 0
Dim sum As Integer = 0
myconn.Open()
reader_sc = mycmd.ExecuteReader()
Do While reader_sc.Read()
sum = sum + reader_sc.item(2)
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