VB3 Using VB Control Property or Variable in SQL Statement

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When building a SQL query, do not include the variable or control name inside the SQL string; instead, you should reference its value. Using the variable or control name inside the SQL string is a mistake. For example, the following code is incorrect:

   Dim ds As Dynaset
      ds.FindFirst "NameField = Text1.Text"    'this code is incorrect
				

This code is trying to create a dynaset that finds the first occurrence of the contents of Text1 in a field called NameField. Although the code will not produce an error, it will not find the desired value. It will search for the first occurrence of the string "Text1.Text" not the value of the Text1.Text control property.

The criteria being sought is a string, so the programmer must use string concatenation rules to build the criteria string. The following gives the correct version of the code example:

   Dim ds As Dynaset
      ds.FindFirst "NameField = '" & Text1.Text & "'"
				

The ampersand (&) operator concatenates the strings together correctly. Also, in SQL syntax, you need to enclose string data in single quotation marks to differentiate strings from variables.

If you think the corrected version looks confusing with all the single and double quotation marks, you can assign the criteria to a string. Then use Debug.Print to view the contents of the string. The following is the same example enhanced to take advantage of the debug window:

   Dim ds As Dynaset
   Dim SQL$ as String
      SQL$ = "NameField = '" & Text1.Text & "'"
      Debug.Print SQL$
      ds.FindFirst SQL$
				

If Text1 contains the string "Wilson," the Debug windows displays:

   NameField = 'Wilson'
				

If the data type of a field is a number instead of a string, don't enclose the value being sought in single quotation marks. For example, use the following code to create a dynaset that finds the first occurrence of a zip code in a field called ZipCodeField where the ZipCodeField data type is not a string:

   Dim ds As Dynaset
   Dim ZipCodeVar as Double
   Dim SQL$ as String
      ZipCodeVar = 98052
      SQL$ = "ZipCodeField = " & ZipCodeVar    'This line builds the string
      Debug.Print SQL$
      ds.FindFirst SQL$