ACC95: Advanced Topics Questions and Answers (137349)

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1. Q. How can I create an expression to extract a portion of a text field?
   
   A. To extract a portion of a text field, use expressions that contain the Left(), Right(), InStr(), and Mid() functions. These expressions are commonly used in the Update To line of an update query to place a portion of a larger field into a new field.
   
   For example, to extract the name "John" from a field containing the name "John Doe," use the following expression:
   

             Left([FullName],InStr(1,[FullName]," ")-1)
   						

   
   and to extract the name "Doe" from the name "John Doe," use the following expression:
   

             Right(Trim([FullName]),Len(Trim([FullName]))-
             InStr(1,[FullName]," "))
   						

   
   For additional information about parsing character strings, see 115915.
2. Q. How can I create an expression to return a value from a table or query using the DLookup() function?
   
   A. With the DLookup() function, you can return a value from a specified set of records, such as a table or query. The syntax of the Dlookup() function is as follows:
   

             DLookup(<expression>, <domain> [, <criteria>] )
   						

   
   The function has the following three arguments:
   
   
   • <Expression>: Identifies the field that contains the data in the domain that you want returned
   • <Domain>: Identifies the table or query that contains the data you want returned
   • <Criteria>: An optional string expression, similar to a WHERE clause in an SQL statement, that restricts the range of data used in the function
   The DLookup() function returns one value from a single field even if more than one record satisfies the criteria. If no record satisfies the criteria or if the domain contains no records, the DLookup() function returns a null.
   
   For additional information about using the DLookup() function, see 136122.
3. Q. How can I calculate date/time data to display specific dates or elapsed time?
   
   A. Microsoft Access stores the Date/Time data type as a double- precision, floating-point number (up to 15 decimal places). The integer portion of the double-precision number represents the date; the decimal portion represents the time. Because a date/time value is stored as a double-precision number, you may receive incorrect formatting results when you try to display specific dates or calculate elapsed time greater than 24 hours.
   
   For additional information about calculating date/time data, see 88657.
4. Q. How do I create synchronized combo boxes?
   
   A. With synchronized combo boxes, you can make a selection in combo box 1, which then filters combo box 2 to list only items related to the selection in combo box 1. For a detailed example of creating synchronized combo boxes, see Q98660.
5. Q. Can I open multiple copies of the same form?
   
   A. Yes, in Microsoft Access for Windows 95, you can open multiple instances of the same form. Opening multiple instances of a form gives you the flexibility to work on more than one record at once. For example, in an Order Entry program, you can start taking an order, pause and take a second order, and then return to the first order without losing any data.
   
   For additional information about opening multiple instances of a form, see 135369.