Question

I was wondering if you could take a look at my code for date comparison on Delphi.

Code snippet in DELPHI:-

        // SQL QUERY to gather member information.
           DMS.ADOQuery1.SQL.Clear;
           DMS.ADOQuery1.SQL.Add('select HPFROMDT, HPthruDt, MEMBERKEY, MEMBHPKEY, OPFROMDT, OPTHRUDT, HPCODEKEY' +
                                 ' from MEMBHP' +
                                 ' where MEMBERKEY = ''' + MembKey + '''   and OPFROMDT <= ''' + date_request + ''' and OPTHRUDT > ''' + date_request +''' '

Script snippet in SQL:-

SELECT [MEMBHPKEY]
      ,[MEMBERKEY]
      ,[CURRHIST]
      ,[HPFROMDT]
      ,[OPFROMDT]
      ,[OPTHRUDT]
      ,[HPCODEKEY]
      ,[HPOPTIONKEY]

  FROM [main].[dbo].[*****]

  where MEMBERKEY = '1234567' and OPFROMDT <= '2007-08-01' and OPTHRUDT > '2007-08-01'

The SQL script obviously compares a constant date value with the extracted date values. And it works!

However, the Delphi code doesn’t work. The error message

Conversion failed when converting character string to smalldatetime
date type.

I believe there has to be some kind of conversion technique for Delphi that should allow me to convert into the right variable type…. Any ideas?

I extract date_request as a string variable from a text file….

  for i := 11 to length(buffer) do
                        begin
                             DT_request := DT_request + buffer[i];
                        end;

Answer 1

The extraction process was picking up a garbage ‘*’ value at the end of the date. This was the problem during date comparison in SQl.

I used

Showmessage(DMS.ADOQuery1.SQL[0]);

and it showed me that the date_request was actually resulting into a ‘20070815*’… Once I figured that out, it was an easy fix. Remove the ‘*’ and compare just as I did previously.

// SQL QUERY to gather member information.
DMS.ADOQuery1.SQL.Clear;
DMS.ADOQuery1.SQL.Add('select HPFROMDT, HPthruDt, MEMBERKEY, MEMBHPKEY, OPFROMDT, OPTHRUDT, HPCODEKEY' +
                       ' from MEMBHP' +
                       ' where MEMBERKEY = ''' + MembKey + '''   and OPFROMDT <= ''' + date_request + ''' and OPTHRUDT > ''' + date_request +''' '