How to: Build SQL Statements That Include Variables and Controls

When working with Data Access Objects (DAO) or ActiveX Data Objects (ADO), you may need to construct an SQL statement in code. This is sometimes referred to as taking your SQL code "inline." For example, if you are creating a new QueryDef object, you must set its SQL property to a valid SQL string. But if you are using an ADO Recordset object, you must set its Source property to a valid SQL string.

The easiest way to construct an SQL statement is to create a query in the query design grid, switch to SQL view, and copy and paste the corresponding SQL statement into your code.

Often a query must be based on values that the user supplies, or values that change in different situations. If this is the case, you need to include variables or control values in your query. The Microsoft Access database engine processes all SQL statements, but not variables or controls. Therefore, you must construct your SQL statement so that Access first determines these values and then concatenates them into the SQL statement that is passed to the Microsoft Access database engine.

Building SQL Statements with DAO

The following example shows how to create a QueryDef object with a simple SQL statement. This query returns all orders from an Orders table that were placed after March 31, 2006:

  Public Sub GetOrders()
Dim dbs As DAO.Database
Dim qdf As DAO.QueryDef
Dim strSQL As String
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate >#3-31-2006#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)
End Sub

The next example creates the same QueryDef object by using a value stored in a variable. Note that the number signs (#) that denote the date values must be included in the string so that they are concatenated with the date value.

  Dim dbs As Database, qdf As QueryDef, strSQL As String
Dim dteStart As Date
dteStart = #3-31-2006#
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate" _
    & "> #" & dteStart & "#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)

The following example creates a QueryDef object by using a value in a control called OrderDate on an Orders form. Note that you provide the full reference to the control, and that you include the number signs (#) that denote the date within the string.

  Dim dbs As Database, qdf As QueryDef, strSQL As String
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate" _
    & "> #" & Forms!Orders!OrderDate & "#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)

Building SQL Statements with ADO

In this section, you will build the same statements as in the previous section, but this time using ADO as the data access method.

The following example shows how to create a QueryDef object with a simple SQL statement. This query returns all orders from an Orders table that were placed after March 31, 2006:

  Dim dbs As Database, qdf As QueryDef, strSQL As String
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate >#3-31-2006#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)

The next example creates the same QueryDef object by using a value stored in a variable. Note that the number signs (#) that denote the date values must be included in the string so that they are concatenated with the date value.

  Dim dbs As Database, qdf As QueryDef, strSQL As String
Dim dteStart As Date
dteStart = #3-31-2006#
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate" _
    & "> #" & dteStart & "#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)

The following example creates a QueryDef object by using a value in a control called OrderDate on an Orders form. Note that it provides the full reference to the control, and that it includes the number signs that denote the date within the string.

  Dim dbs As Database, qdf As QueryDef, strSQL As String
Set dbs = CurrentDb
strSQL = "SELECT * FROM Orders WHERE OrderDate" _
    & "> #" & Forms!Orders!OrderDate & "#;"
Set qdf = dbs.CreateQueryDef("SecondQuarter", strSQL)