vb.net 下的sql多表查詢問題
阿新 • • 發佈：2019-02-17
前一陣子在做一個關於配件維修程式的專案
技術選型為vb.Net 和access資料庫
資料庫的結構是這樣的
分別有客戶表，機器表，配件表三個基本資訊表
將客戶和機器資訊對應形成客戶機器表，為客戶機器表中的機器新增配件形成機器配件表，像機器配件表裡加維修時間形成配件維修表
在一個datagridview中我首先想實現的功能是統計客戶的機器數
sql 語句是這麼寫的
還是沒有實現一次sql實現，在研究還有什麼好的方法，還有第一次讀取的結果加在第二次後面的In 會提高效率，但資料量不是很大，並沒有寫
技術選型為vb.Net 和access資料庫
資料庫的結構是這樣的
分別有客戶表，機器表，配件表三個基本資訊表
將客戶和機器資訊對應形成客戶機器表，為客戶機器表中的機器新增配件形成機器配件表，像機器配件表裡加維修時間形成配件維修表
在一個datagridview中我首先想實現的功能是統計客戶的機器數
sql 語句是這麼寫的
</pre><pre name="code" class="sql">select 客戶表.ID as ID,客戶表.姓名,count(機器客戶表.ID) as 機器數,客戶表.電話 as 客戶電話,客戶表.手機 as 客戶手機,客戶表.聯絡地址 as 客戶地址,客戶表.備註 as 備註
from 客戶表 left join 機器客戶表 on 客戶表.ID=機器客戶表.客戶號 group by 客戶表.ID,客戶表.姓名,客戶表.電話,客戶表.手機,客戶表.聯絡地址,客戶表.備註 而後再連表中join 配件表後，隨著記錄的增加，機器數目將會發生變化
而且accees 不支援distinct 函式
然後我採取的解決方案是
Public Function willPjCount(ByVal khId As String) As String '返回即將維修配件數量 On Error GoTo ErrorHandler Dim con = New OleDbConnection(Autumn_CString1) Dim Sql As String willPjCount = 0 Sql = "select sum(iif(DateDiff('d',date(),配件機器表.提醒時間)>0 and DateDiff('d',date(),配件機器表.提醒時間)<配件表.預警時間, 1,0)) as 即將維修配件數" ' ''sqlshowJqData = sqlshowJqData & "機器客戶表.備註 as 備註" Sql = Sql & " from 客戶表,機器客戶表,配件機器表,配件表 where 客戶表.ID=機器客戶表.客戶號 and 配件機器表.機器ID = 機器客戶表.ID and 配件表.ID =配件機器表.配件ID " & khId con.Open() Dim cmd = New OleDbCommand(Sql, con) Dim myreader As OleDbDataReader = cmd.ExecuteReader While myreader.Read If myreader("即將維修配件數").GetType.ToString() = "System.Double" Then willPjCount = myreader("即將維修配件數") End If End While cmd.Dispose() con.Close() Exit Function ErrorHandler: MsgBox("錯誤號:" & Err.Number & vbCrLf & +Err.Description, vbExclamation + vbOKOnly, "其他錯誤!") Exit Function End Function
Public Function OutPjCount(ByVal khId As String) As String '返回過期維修配件數量 On Error GoTo ErrorHandler Dim con = New OleDbConnection(Autumn_CString1) Dim Sql As String OutPjCount = 0 Sql = "select sum(iif(DateDiff('d',date(),配件機器表.提醒時間)<0 , 1,0)) as 過期維修配件數" ' ''sqlshowJqData = sqlshowJqData & "機器客戶表.備註 as 備註" Sql = Sql & " from 客戶表,機器客戶表,配件機器表 where 客戶表.ID=機器客戶表.客戶號 and 配件機器表.機器ID = 機器客戶表.ID " & khId con.Open() Dim cmd = New OleDbCommand(Sql, con) Dim myreader As OleDbDataReader = cmd.ExecuteReader While myreader.Read OutPjCount = myreader("過期維修配件數") End While cmd.Dispose() con.Close() Exit Function ErrorHandler: 'MsgBox("錯誤號:" & Err.Number & vbCrLf & "錯誤內容:系統基本資訊" & khId & "設定不完整，請新增供應商名稱", vbExclamation + vbOKOnly, "其他錯誤!") Exit Function End Function
<span style="font-family: Arial, Helvetica, sans-serif; background-color: rgb(255, 255, 255);">而後採取的解決方案是在myread裡二次讀取</span><span style="font-family: Arial, Helvetica, sans-serif;"> </span><span style="font-family: Arial, Helvetica, sans-serif;"> willPj = willPjCount("and 客戶表.ID =" & myreader("ID"))</span> outPj = OutPjCount("and 客戶表.ID =" & myreader("ID"))
.Rows(i).Cells(4).Value = willPj
.Rows(i).Cells(5).Value = outPj
If Convert.ToInt32(willPj) > 0 Then
.Rows(i).Cells(4).Style.BackColor = Color.Red
End If
If Convert.ToInt32(outPj) > 0 Then
.Rows(i).Cells(5).Style.BackColor = Color.Blue
End If
.Rows(i).Cells(6).Value = myreader("客戶電話")
.Rows(i).Cells(7).Value = myreader("客戶手機")
.Rows(i).Cells(8).Value = myreader("客戶地址")
.Rows(i).Cells(9).Value = myreader("備註")但在記錄數超過20個時，就會出線未知的錯誤
最後的解決方案
Dim cmd = New OleDbCommand(Sql, con)
Dim myreader As OleDbDataReader = cmd.ExecuteReader
Dim i As Integer
Dim idI As New Dictionary(Of String, Integer)
Dim outPj As String = ""
Dim willPj As String = ""
Dim tempId As Integer
Dim maxId As Integer
i = 0
With datagridview_t
.Columns.Clear()
客戶資訊列表頭初始化(datagridview_t)
While (myreader.Read)
.Rows.Add()
.Rows(i).Cells(1).Value = myreader("ID")
idI.Add(myreader("ID"), i)
.Rows(i).Cells(2).Value = myreader("姓名")
.Rows(i).Cells(3).Value = myreader("機器數")
.Rows(i).Cells(6).Value = myreader("客戶電話")
.Rows(i).Cells(7).Value = myreader("客戶手機")
.Rows(i).Cells(8).Value = myreader("客戶地址")
.Rows(i).Cells(9).Value = myreader("備註")
i = i + 1
End While
maxId = i - 1
Sql = "select 客戶表.ID as ID,sum(iif(DateDiff('d',date(),配件機器表.提醒時間)>-7 and DateDiff('d',date(),配件機器表.提醒時間)<配件表.預警時間, 1,0)) as 即將維修配件數,sum(iif(DateDiff('d',date(),配件機器表.提醒時間)<-7 , 1,0)) as 過期維修配件數"
Sql = Sql & " from 客戶表,機器客戶表,配件機器表,配件表 where 客戶表.ID=機器客戶表.客戶號 and 配件機器表.機器ID = 機器客戶表.ID and 配件表.ID =配件機器表.配件ID group by 客戶表.ID"
cmd = New OleDbCommand(Sql, con)
myreader = cmd.ExecuteReader
i = 0
While (myreader.Read)
tempId = i
If tempId <> 0 Then
tempId += 1
End If
i = idI(myreader("ID"))
For j = tempId To i - 1
.Rows(j).Cells(4).Value = 0
.Rows(j).Cells(5).Value = 0
Next
.Rows(i).Cells(4).Value = Convert.ToInt32(myreader("即將維修配件數"))
.Rows(i).Cells(5).Value = Convert.ToInt32(myreader("過期維修配件數"))
If .Rows(i).Cells(4).Value > 0 Then
.Rows(i).Cells(4).Style.BackColor = Color.Red
End If
If .Rows(i).Cells(5).Value > 0 Then
.Rows(i).Cells(5).Style.BackColor = Color.Blue
End If
willPj = willPjCount("and 客戶表.ID =" & myreader("ID"))
outPj = OutPjCount("and 客戶表.ID =" & myreader("ID"))
.Rows(i).Cells(4).Value = willPj
.Rows(i).Cells(5).Value = outPj
If Convert.ToInt32(willPj) > 0 Then
.Rows(i).Cells(4).Style.BackColor = Color.Red
End If
If Convert.ToInt32(outPj) > 0 Then
.Rows(i).Cells(5).Style.BackColor = Color.Blue
End If
.Rows(i).Cells(6).Value = myreader("客戶電話")
.Rows(i).Cells(7).Value = myreader("客戶手機")
.Rows(i).Cells(8).Value = myreader("客戶地址")
.Rows(i).Cells(9).Value = myreader("備註")
End While
For j = i + 1 To maxId
.Rows(j).Cells(4).Value = 0
.Rows(j).Cells(5).Value = 0
Next
.Rows.Add()
End With 還是沒有實現一次sql實現，在研究還有什麼好的方法，還有第一次讀取的結果加在第二次後面的In 會提高效率，但資料量不是很大，並沒有寫