表达式中未定义的函数“ Nz”

美克美克

我已经用Google在搜索了这个错误之后，我还没有得出我为什么会收到这个错误的结论。我试图用一些数据填充DataGridView。这是我的代码。
* v9 ], {! G$ @$ A) nPrivate Sub LoadGrid()    Dim cmd As New OleDbCommand    Dim dt As DataTable    With cmd        .CommandText = "project_master_query"        .CommandType = CommandType.StoredProcedure        .Connection = New OleDbConnection(My.Settings.cnnString)    End With    dt = GetData(cmd)    dgvData.DataSource = dtEnd SubPrivate Function GetData(ByVal cmd As OleDbCommand) As DataTable    Dim dt As New DataTable    Using cmd.Connection        cmd.Connection.Open()        dt.Load(cmd.ExecuteReader(CommandBehavior.CloseConnection))    End Using    Return dtEnd Function查询存储在Access中的“ project_master_query”。
6 i- o! T1 e! n  h+ m8 M: Q9 V+ X; }                SELECT project_master.*,location_master.LocationName,   project_currentmilestonedef.MilestoneDefID,    project_currentmilestonedef.MilestoneName,project_regions.RegionName,   owner_fullname.FullName AS OwnerFullName,designer_fullname.FullName AS DesignerFullName,   project_issuecount.HasOpenIssues,project_updated_closedate.UpdatedCloseDate,    project_bonusdays.BonusDays,project_bonusdays.IsGreen,project_bonusdays.IsYellow,    project_bonusdays.IsRed,checklist_days_perproject_defined_1.Week1,    checklist_days_perproject_defined_1.Week2,checklist_days_perproject_defined_1.Week3,    checklist_days_perproject_defined_1.Week4,project_issueduration.ProjectIssueDurationDays,    project_active_status.ProjectIsOpen,project_requirement_status.RequirementStatusName,    priority_def.PriorityShortName    FROM project_requirement_status     RIGHT JOIN (project_regions     RIGHT JOIN (priority_def RIGHT JOIN (location_master     RIGHT JOIN ((((checklist_days_perproject_defined AS checklist_days_perproject_defined_1     RIGHT JOIN ((((((((contacts_fullname AS designer_fullname     RIGHT JOIN (contacts_fullname AS owner_fullname     RIGHT JOIN project_master ON owner_fullname.ContactID = project_master.ContactOwner)     ON designer_fullname.ContactID = project_master.ContactDesigner)     LEFT JOIN project_issuecount     ON project_master.ProjectID = project_issuecount.ProjectID)     LEFT JOIN project_currentmilestonedef     ON project_master.ProjectID = project_currentmilestonedef.ProjectID)     LEFT JOIN project_within_benchmark_week1     ON project_master.ProjectID = project_within_benchmark_week1.ProjectID)     LEFT JOIN project_within_benchmark_week2     ON project_master.ProjectID = project_within_benchmark_week2.ProjectID)     LEFT JOIN project_within_benchmark_week3     ON project_master.ProjectID = project_within_benchmark_week3.ProjectID)     LEFT JOIN project_updated_closedate     ON project_master.ProjectID = project_updated_closedate.ProjectID)     LEFT JOIN checklist_days_perproject_defined     ON project_master.ProjectID = checklist_days_perproject_defined.ProjectID)     ON checklist_days_perproject_defined_1.ProjectID = project_master.ProjectID)     LEFT JOIN project_issueduration     ON project_master.ProjectID = project_issueduration.ProjectID)     LEFT JOIN project_active_status     ON project_master.ProjectID = project_active_status.ProjectID)        LEFT JOIN project_bonusdays ON project_master.ProjectID = project_bonusdays.ProjectID)     ON location_master.LocationID = project_master.Location)     ON priority_def.PriorityDefID = project_master.ProjectPriority)     ON project_regions.RegionID = project_master.Region)     ON project_requirement_status.RequirementStatusID = project_master.RequirementStatus;如你所见，查询中根本没有Nz，所以我不明白为什么会这样。一旦调用dt.Load，这个错误就会发生。
                                                               
& b  o! N$ O- ?. W    解决方案:                                                               
                                                                该Nz在许多连接之一中引用的视图/查询中，函数最有可能。您必须仔细阅读所有这些内容。
4 L6 _! F4 {+ I: x$ i由于Nz()是Access应用程序(而不是Access因此，当您尝试从驱动程序)的功能时Access当应用程序外部使用时，它将失败。您可以替换它Nz与IIf(IsNull()结构。
9 n9 ~2 v5 [1 _" Z请参阅IIf和的文档IsNull
放在一起:
9 v' e1 d( V% @: y% M8 BNz(expr,[valueifnull])
+ {0 D3 h0 U! n( v变成
IIf(IsNull(expr),valueifnull,valueifnotnull)
例子
6 d" Z# _' f/ o' R( E8 G( N. z: G默认： Nz(tbl.A) => IIf(IsNull(tbl.A),'',tbl.A)
6 E. O- }! J' G) w后备功能： Nz(tbl.A,tbl.B) => IIf(IsNull(tbl.A),tbl.B,tbl.A)