Alias variable in MapBasic

Question

I'm having a bit of trouble with the Alias variable in MapBasic. In short, I have a table where I was to group by a specific column. Then I want to run through each unique value from the grouped table through the original one and combine each one. So I have a table of cities with a column of which country each city is in. My program gives the user to choose a table and a column within that table to gorup by. Then it basically goes like this:

Dim aSelection, aGrouped as Alias 

Selection = selectedTable & "." & selectedColumn

Select * from selectedTable into Temp_GroupedTable Group By selectedColumn

aGrouped = Temp_GroupedTable & "." & selectedColumn

So a) is this code correct? b) How can I fetch the data from each row in the Temp_GroupedTable so that I can compare it with the values in the original table? I currently have this general setup within a loop:

Fetch rec i from Temp_GroupedTable

Select * from selectedTable into New_Temp_TAB Where aSelection = aGrouped

Objects Combine

I know there is something wrong... But I don't know how to fix it. Any ideas?

Answer 1

Try this:

Dim aSelection, aGrouped as Alias
Dim sGrouped As String

aSelection = selectedTable & "." & selectedColumn
Select * from selectedTable 
   into Temp_GroupedTable 
   Group By aSelection

aGrouped = "Temp_GroupedTable." & selectedColumn

Fetch First from Temp_GroupedTable
Do Until EOT(Temp_GroupedTable)
   aGrouped = sGrouped
   Select * from selectedTable 
      into New_Temp_TAB 
      Where aSelection = sGrouped

‘**  Objects Combine ...

   Fetch First from Temp_GroupedTable
Loop

I changed your first selection a bit and also the assignment of the aGrouped alias variable. And then I made some changes to your loop. I’m not entirely sure what more you want to do within the loop.

I’m not entirely sure about this line: Where aSelection = aGrouped

You might need to read the value into a string or numeric value first. But give it a go and let us know

Answer 2

Thanks for the help @Peter! I ended up using the following code which did what I needed:

Sub Process

Dim aGrouped as Alias

Print "Object Combiner Loaded!"

Select * from selectedTable into Temp_GroupedTable Group By selectedColumn
Print "Grouping Successful"

'*** Groups by user selected column
aSelection = selectedTable & "." & selectedColumn
Select * from selectedTable 
    into Temp_GroupedTable 
    Group By aSelection

aGrouped = "Temp_GroupedTable." & selectedColumn

Fetch First from Temp_GroupedTable  '*** Fetchs first row from grouped table
'*** Runs through table to combine objects by each individual value
Do Until EOT(Temp_GroupedTable)
    sGrouped = aGrouped
    Select * from selectedTable 
        Where aSelection = sGrouped
    Objects Combine Data selectedColumn = sGrouped 'Retains value of 
                                                   'selected column
    Fetch Next from Temp_GroupedTable
Loop

End Sub