如何檢查表中是否爲空值？

Question

使用MS ACCESS 2003

如何檢查訪問數據庫中是否爲空值？

我的代碼。

Public Function DateToString(dte As Date) As String 
Dim d As String 
Dim m As String 
Dim y As String 
d = Day(dte) 
m = Month(dte) 
y = Year(dte) 
If Len(d) = 1 Then d = "0" & d 
If Len(m) = 1 Then m = "0" & m 
DateToString = y & m & d 
End Function 


Public Function StringToDate(txt As String) As Date 
Dim dte As String 
dte = Left(txt, 4) & "-" & Mid(txt, 5, 2) & "-" & Right(txt, 2) 
StringToDate = CDate(dte) 
End Function 




sql1 = "CREATE TABLE MOI (PreDate varchar(50))" 
sql2 = "INSERT INTO MOI values('" & StringToDate(rsCardEvent1.Fields("PreDate")) "')" 

從上面的功能，我想檢查，如果不爲空，然後我的代碼，否則沒有必要。

需要VB 6.0代碼幫助嗎？

Answer 1

要在數據集字段檢查空

If (txt & "") = "" Then 
    ' txt is Null or empty 
End If 

Answer 2

如果該項目實際上未來是一個字符串，然後做：

If IsNull(rs("colname")) Then 
    'Field contains a Null Value 
Else 
    'Field does 'not' contain a Null Value 
End If 

檢查null或空字符串：

if not txt is vbNullString then 
    ' code here 
end if