Check if access table exists

I want to log web site visits' IP, datetime, client and refferer data to access database but I'm planning to log every days log data in separate tables in example logs for 06.06.2010 will be logged in 2010_06_06 named table. When date is changed I'll cre开发者_开发技巧ate a table named 2010_06_07. But the problem is if this table is already created.

Any suggestions how to check if table exists in Access?

You can use the hidden system table MSysObjects to check if a table exists:

If Not IsNull(DlookUp("Name","MSysObjects","Name='TableName'")) Then
    'Table Exists

However, I agree that it is a very bad idea to create a new table every day.

EDIT: I should add that tables have a type 1, 4 or 6 and it is possible for other objects of a different type to have the same name as a table, so it would be better to say:

If Not IsNull(DlookUp("Name","MSysObjects","Name='TableName' And Type In (1,4,6)")) Then
    'Table Exists

However, it is not possible to create a table with the same name as a query, so if you need a look up to test for a name, it may be best to add 5, that is query, to the Type list.

Here's another solution, will be a bit faster than looping over all of the tables.

Public Function doesTableExist(strTableName As String) As Boolean
    Dim db As DAO.Database
    Dim td As DAO.TableDef
    Set db = CurrentDb
    On Error Resume Next
    Set td = db.TableDefs(strTableName)
    doesTableExist = (Err.Number = 0)
    Err.Clear
End Function

I tested various methods for finding out if a table exists several years ago. Here is the code for all of them as I implemented, including my simple test routine.

    Public Function TableExists(strTableName As String, Optional ysnRefresh As Boolean, Optional db As DAO.Database) As Boolean
    ' Originally Based on Tony Toews function in TempTables.MDB, http://www.granite.ab.ca/access/temptables.htm
    ' Based on testing, when passed an existing database variable, this is the fastest
    On Error GoTo errHandler
      Dim tdf As DAO.TableDef
    
      If db Is Nothing Then Set db = CurrentDb()
      If ysnRefresh Then db.TableDefs.Refresh
      Set tdf = db(strTableName)
      TableExists = True
    
    exitRoutine:
      Set tdf = Nothing
      Exit Function
    
    errHandler:
      Select Case Err.Number
        Case 3265
          TableExists = False
        Case Else
          MsgBox Err.Number & ": " & Err.Description, vbCritical, "Error in mdlBackup.TableExists()"
      End Select
      Resume exitRoutine
    End Function
    
    Public Function TableExists2(strTableName As String, Optional ysnRefresh As Boolean, Optional db As DAO.Database) As Boolean
    On Error GoTo errHandler
      Dim bolCleanupDB As Boolean
      Dim tdf As DAO.TableDef
    
      If db Is Nothing Then
         Set db = CurrentDb()
         bolCleanupDB = True
      End If
      If ysnRefresh Then db.TableDefs.Refresh
      For Each tdf In db.TableDefs
        If tdf.name = strTableName Then
           TableExists2 = True
           Exit For
        End If
      Next tdf
    
    exitRoutine:
      Set tdf = Nothing
      If bolCleanupDB Then
         Set db = Nothing
      End If
      Exit Function
    
    errHandler:
      MsgBox Err.Number & ": " & Err.Description, vbCritical, "Error in mdlBackup.TableExists1()"
      Resume exitRoutine
    End Function
    
    Public Function TableExists3(strTableName As String, _
         Optional db As DAO.Database) As Boolean
    ' Based on testing, when NOT passed an existing database variable, this is the fastest
    On Error GoTo errHandler
      Dim strSQL As String
      Dim rs As DAO.Recordset
    
      If db Is Nothing Then Set db = CurrentDb()
      strSQL = "SELECT MSysObjects.Name FROM MSysObjects "
      strSQL = strSQL & "WHERE MSysObjects.Name=" & Chr(34) & strTableName & Chr(34)
      strSQL = strSQL & " AND MSysObjects.Type=6;"
      Set rs = db.OpenRecordset(strSQL)
      TableExists3 = (rs.RecordCount <> 0)
      
    exitRoutine:
      If Not (rs Is Nothing) Then
         rs.Close
         Set rs = Nothing
      End If
      Exit Function
    
    errHandler:
      MsgBox Err.Number & ": " & Err.Description, vbCritical, _
         "Error in TableExists1()"
      Resume exitRoutine
    End Function
    
    Public Sub TestTableExists(strTableName As String, intLoopCount As Integer)
      Dim dteStart As Date
      Dim i As Integer
      Dim bolResults As Boolean
      
      dteStart = Now()
      For i = 0 To intLoopCount
        bolResults = TableExists(strTableName, , CurrentDB())
      Next i
      Debug.Print "TableExists (" & intLoopCount & "): " & Format(Now() - dteStart, "nn:ss")
    
      dteStart = Now()
      For i = 0 To intLoopCount
        bolResults = TableExists2(strTableName, , CurrentDB())
      Next i
      Debug.Print "TableExists2 (" & intLoopCount & "): " & Format(Now() - dteStart, "nn:ss")
    
      dteStart = Now()
      For i = 0 To intLoopCount
        bolResults = TableExists3(strTableName, CurrentDB())
      Next i
      Debug.Print "TableExists3 (" & intLoopCount & "): " & Format(Now() - dteStart, "nn:ss")
    End Sub

I have found querying system tables or tabledefs to be unreliable and introduce unpredictable behaviour in scripts where tables get regularly created and dropped.

Based on my results, my hypothesis is that these tables aren't necessarily updated at the exact instant a CREATE or DROP is executed, or that concurrency issues are preventing me from getting an accurate result.

I've found the following method to be more reliable:

Public Function TableExists(theDatabase As Access.Application, _
    tableName As String) As Boolean

    ' Presume that table does not exist.
    TableExists = False

    ' Define iterator to query the object model.
    Dim iTable As Integer

    ' Loop through object catalogue and compare with search term.
    For iTable = 0 To theDatabase.CurrentData.AllTables.Count - 1
        If theDatabase.CurrentData.AllTables(iTable).Name = tableName Then
            TableExists = True
            Exit Function
        End If
    Next iTable

End Function

There should be no runtime issue iterating unless there is an staggeringly enormous collection of tables.

This question is quite old but I found that no answer is satisfying, because:

• they do not handle the case of "bad" linked tables, where the linked table points to a non existing db or table.
• since linked tables are potentially huge, we must be able to check them with a fast query.

So here is my simple but more complete solution:

    Function isTableOk(tblName As String) As Boolean
    'works with local or linked tables
        Dim db As DAO.Database, rs As DAO.Recordset
        Dim sSql As String
        sSql = "SELECT TOP 1 ""xxx"" AS Expr1 FROM [" & tblName & "]"
        
        On Error Resume Next
        Err.Clear
        Set db = CurrentDb
        Set rs = db.OpenRecordset(sSql)
        isTableOk = (Err.Number = 0)
        rs.Close
    End Function

You can even check table in an external Access db with this version:

    Function isTableOk(tblName As String, Optional dbName As String) As Boolean
    'works with local or linked tables, or even tables in external db (if dbName is provided)
    
        Dim db As DAO.Database, rs As DAO.Recordset
        Dim sSql As String
        
        Set db = CurrentDb
        sSql = "SELECT TOP 1 'xxx' AS Expr1 FROM [" & tblName & "]"
        If Len(dbName) > 0 Then 'external db 
            sSql = sSql & " IN '" & dbName & "'"
        End If
        Err.Clear
        On Error Resume Next
        Set rs = db.OpenRecordset(sSql)
        isTableOk = (Err.Number = 0)
        rs.Close
    End Function