运行时错误'94'无效使用Null [英] Run-time error '94' Invalid use of Null

问题描述

需要有关学生表结构的建议。对于sql server 2005的注册列（数据类型）的兴趣。我还需要使用我的函数声明的数据类型的建议。我的登记列目前有位数据类型。我得到的错误可能是问题。

 公共 功能 GetEnrolled（）作为  Boolean  
 如果 Rs.State = adStateOpen 那么 Rs.Close 
 sql =   SELECT Students.Enrolled From Students WHERE Students.sID ='& vOldIDNumber&  '和students.yrlevel ='& voidYearlevel&  '和students.scourse ='& voidCourse&  '和semester ='& voidSem&  ' 
 Rs.Open sql，RSconn 
 如果 不 Rs.EOF 那么 
 GetEnrolled = Rs （ 0 ）。值
 结束 如果 
 结束 功能 

解决方案

要做的步骤：

1）创建并打开连接

2）创建并打开Recordset对象

3）虽然记录集不是EOF，但读取值

  Dim  oConn  As  ADODB.Connection 
  Dim  sConn  As  字符串 
  Dim  oRst  As  ADODB.Recordset 
  Dim  sSQL  As  字符串 
 
 sConn =  您的连接 
 
 设置 oConn = 新 ADODB.Connection 
 oConn.Open sConn 
 
  Set  oRst =  New  ADODB.Recordset 
 sSQL =  您的查询 
 rstEmployees.Open sSQL，oConn，adOpenStatic， adLockOptimistic，adCmdTable 
 
     不 oRst.EOF 
 MsgBox oRst.Fields（ 0 ）。值
 .MoveNext 
 循环 

查看更多：
Open Method（ADO记录集） ） [ ^ ]

打开和关闭方法示例（VB） [ ^ ]

MoveFirst，MoveLast，MoveNext和MovePrevious Methods Example（VB） [ ^ ]

使用此

 GetEnrolled = IIf（IsNull（Rs（0）.Value），，Rs（0）.Value）

Need advice on the structure of students table..interest on enrolled column(datatype) for sql server 2005. I also need advice on the use of the datatype for which my function is declared. My enrolled column currently has bit datatype. Am getting the error above what could be the problem.

Public Function GetEnrolled() As Boolean
If Rs.State = adStateOpen Then Rs.Close
sql = " SELECT Students.Enrolled From Students WHERE Students.sID='" & vOldIDNumber & "' and students.yrlevel='" & voidYearlevel & "' and students.scourse='" & voidCourse & "' and semester='" & voidSem & "'"
   Rs.Open sql, RSconn
   If Not Rs.EOF Then
   GetEnrolled = Rs(0).Value
   End If
End Function

解决方案

Steps to do:
1) create and open connection
2) create and open Recordset object
3) while recordset not EOF, read values

Dim oConn As ADODB.Connection
Dim sConn As String 
Dim oRst As ADODB.Recordset
Dim sSQL As String

sConn = "Your connection"

Set oConn = New ADODB.Connection
oConn.Open sConn

Set oRst = New ADODB.Recordset
sSQL = "your query"
rstEmployees.Open sSQL, oConn, adOpenStatic, adLockOptimistic, adCmdTable

Do While Not oRst.EOF
    MsgBox oRst.Fields(0).Value
    .MoveNext
Loop

See more:
Open Method (ADO recordset)[^]
Open and Close Methods Example (VB)[^]
MoveFirst, MoveLast, MoveNext, and MovePrevious Methods Example (VB)[^]

Use this

GetEnrolled = IIf(IsNull(Rs(0).Value), "", Rs(0).Value)

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