Delphi & ADO: datetime to string conversion - delphi

I use Delphi 2006 and ADO to connect to a MS Access database. Some of the fields I retrieve are Date fields (in Access formatted as "Medium Date" i.e. 20-Apr-2010) however I have to retrieve them as Strings:
FValue:=FAccessADOQuery.Fields.FieldByName(FIELD_NAME).AsString;
and then the fields are formatted as follows: 4/20/2010.
My question is: when does this formatting take place and how can I customize it? Is it ADO settings (could not find anything there) or the OS (I use Win XP ENG with US locale)? Or maybe it's Delphi?
Thanks!
Lou

the ShortDateFormat and LongTimeFormat variables are used to format an TDateTimeField to string.
you can change the value of theses variables or try something different like this :
Dt :TDateTime;
Ds :String;
begin
//FAccessADOQuery.Fields.FieldByName(FIELD_NAME).AsString
Dt:=FAccessADOQuery.Fields.FieldByName(FIELD_NAME).AsDateTime;
Ds:=FormatDateTime('dd-mmm-yyyy',dt);
end;

Ok, just found it. It's delphi general settings (if missing then the values are taken from the OS):
DateSeparator := '-';
ShortDateFormat := 'dd-mmm-yyyy';
And now the returned value is "20-Apr-2010".

You can retreive the Value as DateTime and use this function to convert it to your format
FValue:=FAccessADOQuery.Fields.FieldByName(FIELD_NAME).AsDateTime;
function DateToMediumDate(const Date: TDate): string;
var
y, m, d: Word;
begin
DecodeDate(Date, y, m , d);
Result := Format('%d-%s-%d', [d, ShortMonthNames[m], y]);
end;

Related

How to include a variable between strings in Delphi?

procedure TForm1.Button1Click(Sender: TObject);
var
xlap,xlbook,xlsheet:variant;
y:integer;
begin
xlap:=createoleobject('excel.application');
xlbook:=xlap.workbooks.add;
xlap.visible:=true;
xlsheet:=xlbook.worksheets.add;
for y:=1 to 50 do
begin
xlsheet.cells[y,2].value:= concat('=IF(A',y,'>6,"Good","Bad")')
inc(y);
end;
end;
That's my code to make an Excel through Delphi. I want to input the IF formula into column B of the Excel, but there is error when I use the concat('=IF(A',y,'>6,"Good","Bad")').
May be I need another way to include y between those strings.
Any suggestion? Thanks before
Delphi has a format statement bit like sprintf printf in c, well nearly
xlsheet.cells[y,2].value:= format('=IF(A%d>6,"Good", "Bad")',[y])
%d is a place holder for an int. Look it up for loads of other stuff.
NB the variables you want to interpolate are assed in an array.
In addition to Tony's answer about Format, here are a couple of other approaches. (Format is great if you have mixed types or many values, but it carries some overhead that might not be needed.)
You can concatenate strings with a simple + - in fact, the Concat documentation says it does the same thing but is faster:
Temp := 'ing';
Str := 'Test' + Temp; // Str = 'Testing'
As your y variable is an integer, you'll need to convert it to a string first (note you don't need to Inc(y);, as the loop will do that already - it's automatically incremented from the starting value to the ending value on each pass through the loop):
for y:=1 to 50 do
begin
xlsheet.cells[y,2].value:= '=IF(A' + IntToStr(y) + '>6,"Good","Bad")';
end;

Locate in Delphi XE2 TADO exception with single quote in search value

Having trouble with Delphi XE2 (update2) using MS SQL 2008 R2 (sp 2) or with MS SQL 2005 (sp4).
form1.ado_m is via the TADO dataset with no parameter check using native 64 sql
var
okd:boolean;
dd:ansistring;
code snippet:
okd:=form1.ado_m.Locate('abcrow',dd,[loCaseInsensitive]);
If the value of dd ends in a single quote (it is converted to '' in the debugger) it gives a exception:
Exception class EOleException with message 'Arguments are of the wrong type, are out of acceptable range, or are in conflict with one another'.
What is strange to me is that is a single quote character is the middle of var dd it works fine.
Workaround?
The problem is caused by the number sign (#) AND quote together in the search value.
Locate use the ADO find method: The value in Criteria may be a string, floating-point number, or date. String values are delimited with single quotes or "#" (number sign) marks (for example, "state = 'WA'" or "state = #WA#").
Try to replace the number sign OR quote character by inserting records.
Another option is to use the OnFilterRecord and filtered property:
...
FSearchValue := 'A1020778014#;]_69BO'''; // private field in TForm1
ado_m.Filtered := true;
try
okd := not ado_m.IsEmpty;
finally
ado_m.Filtered := false;
end;
...
procedure TForm1.ado_mFilterRecord(DataSet: TDataSet;
var Accept: Boolean);
begin
Accept := SameText(DataSet.FieldByName('abcrow').AsString, FSearchValue);
end;

Avoiding Locale Conflicts when storing TDateTime's in Floats?

I got the TDateTime thing fixed by using Floating vars to store them in a file. However, now I face a new problem: Invalid Floating Point - Most likely because of the Comma Separator.
How can I set the default separator in my program? Or is there any other way around?
You can use a TFormatSettings record to specify the decimal separator when you call StrToFloat and FloatToStr. You have to decide what to use and stick to that. Here is sample code with a .
var
d: TDateTime;
s: string;
fs: TFormatSettings;
begin
d := Now();
fs.DecimalSeparator := '.';
s := FloatToStr(d, fs);
end;
Another option would be to use the XML standard date time format. Delphi has some functions in XSBuiltIns to do the conversion from TDateTime to string and back. You will have a time zone offset in the value so if you move your persisted TDateTime from one time zone to another you may have some unwanted behavior. It depends on the usage of the value.
var
d: TDateTime;
s: string;
begin
d := Now();
s := DateTimeToXMLTime(d);
d := XMLTimeToDateTime(s);
end;
As Mikael suggested, there are a many ways to do this. To re-cap you wish to store a TDateTime to a file in textual format and be able to restore this value successfully irrespective of the locale on which the restoration happens.
Option 1
When storing, call FloatToStr, say, but force a '.' for the decimal separator through the TFormatSettings parameter. On restore, use StrToFloat with the same TFormatSettings.
Option 2
Encode the 8 byte TDateTime value using base 64. This has the downside that it renders the value unreadable.
Option 3
Similar to option 1, but encode the TDateTime by calling DateTimeToStr and explicitly passing a TFormatSettings that does not rely on anything in the locale – so do not rely on the locale's date or time separators, instead force your own. To reverse call StrToDateTime with an identical TFormatSettings record.

Help with sending number to Excel 2007 from Delphi 2010 as a string

I'm sending a number to Excel 2007 as a string (Cell.Value := '2,5') using late binding. The actual code is more like:
var CellVal: OLEVariant;
...
CellVal := FloatToStr(2.5); // Regionally formatted.
Cell.Value := CellVal;
On my Excel 97 version, this value will be formatted as "General" by default and will be seen as a number. A customer with Excel 2007 ends up with the cell formatted as "Standard" and Excel appears to see it as a string (it's not right aligned.) Note that I am using the regional settings to format the number and that Excel appears to be using the default regional settings as well.
If the customer just types 2,5 into a cell it accepts it as a number and if he does a copy of the string '2,5' from the clipboard into a cell, it also gets accepted as a number. Does anyone know why the string value sent though the automation interface to Excel ends up as a non-number?
Thanks for any suggestions! Edited to specify the regional decimal separator for the customer is ','.
Since you cannot format comments:
I just did a little test and Excel doesn't want a regional formatted float value as string, it just want a dot as decimal separator.
procedure TForm1.Button1Click(Sender: TObject);
var
App: Variant;
Workbook: Variant;
Worksheet: Variant;
DoubleValue: Double;
begin
App := CreateOleObject('Excel.Application');
Workbook := App.Workbooks.Add;
Worksheet := Workbook.ActiveSheet;
DoubleValue := 1.2;
Worksheet.Range['A1'].Value := DoubleValue; //DoubleValue is a double, excel recognizes a double
Worksheet.Range['A2'].Value := '1.2'; //excel recognizes a double
Worksheet.Range['A3'].Value := '1,2'; //excel recognizes a string
Worksheet.Range['A4'].Value := FloatToStr(1.2); //excel recognizes a string
App.Visible := True;
end;
Keep in mind that I hava a comma as decimal separator.
Probably because you give it a string. Have you tried passing it the float value directly?
Can't explain why the behaviour is different but it would appear to be down to how Excel 2007 interprets the incoming value.
How about setting the format of the cell in code?
Worksheets("Sheet1").Range("A17").NumberFormat = "General"

Getting a Field List from a DBExpress TSQLQuery

I am having a problem getting a list of fields from a query defined at run time by the users of my program. I let my users enter a SQL query into a memo control and then I want to let them go through the fields that will return and do such things as format the output, sum column values and so forth. So, I have to get the column names so they have a place to enter the additional information.
I would do fine if there were no parameters, but I also have to let them define filter parameters for the query. So, if I want to set the parameters to null, I have to know what the parameter's datatype is.
I am using Delphi 2006. I connect to a Firebird 2.1 database using the DBExpress component TSQLConnection and TSQLQuery. Previously, I was successful using:
for i := 0 to Qry.Params.Count - 1 do Qry.Params[i].value := varNull;
I discovered I had a problem when I tried to use a date parameter. It was just a coincidence that all my parameters up until then had been integers (record IDs). It turns out that varNull is just an enumerated constant with a value of 1 so I was getting acceptable results (no records) was working okay.
I only need a list of the fields. Maybe I should just parse the SELECT clause of the SQL statement. I thought setting Qry.Prepared to True would get me a list of the fields but no such luck. It wants values for the parameters.
If you have an idea, I would sure like to hear it. Thanks for any help.
Replied again 'coz I'm interested. My methods works (with my queries) because they have been pre-defined with the params' datatypes preset to the correct type:)
I'm not sure how you are expecting the query to know or derive the datatype of the param given that you are not even selecting the field that it operates against.
So I think your query setup and user input method will need more attention. I've just looked up how I did this a while ago. I do not use a parameterised query - I just get the "parameter values" from the user and put them directly into the SQL. So your sql would then read:
SELECT s.hEmployee, e.sLastName
FROM PR_Paystub s
INNER JOIN PR_Employee e ON e.hKey = s.hEmployee
WHERE s.dtPaydate > '01/01/2008'
therefore no parameter type knowledge is necessary. Does not stop your users entering garbage but that goes back to input control :)
Although a slightly different dataset type this is what I use with TClientDataset simple and effective :)
for i := 0 to FilterDataSet.Params.Count -1 do
begin
Case FilterDataSet.Params.Items[i].Datatype of
ftString:
ftSmallint, ftInteger, ftWord:
ftFloat, ftCurrency, ftBCD:
ftDate:
ftTime:
ftDateTime:
.
.
.
end;
end;
can you not do something similar with the query?
You guys are making this way too hard:
for i := 0 to Qry.Params.Count - 1 do begin
Qry.Params[i].Clear;
Qry.Params[i].Bound := True;
end;
I'm not sure what version of Delphi you are using. In the Delphi 2006 help under Variant Types, it says:
Special conversion rules apply to the
Borland.Delphi.System.TDateTime type
declared in the System unit. When a
Borland.Delphi.System.TDateTime is
converted to any other type, it
treated as a normal Double. When an
integer, real, or Boolean is converted
to a Borland.Delphi.System.TDateTime,
it is first converted to a Double,
then read as a date-time value. When a
string is converted to a
Borland.Delphi.System.TDateTime, it is
interpreted as a date-time value using
the regional settings. When an
Unassigned value is converted to
Borland.Delphi.System.TDateTime, it is
treated like the real or integer value
0. Converting a Null value to Borland.Delphi.System.TDateTime raises
an exception.
The last sentence seems important to me. I would read that as varNull cannot be converted to a TDateTime to put into the field, and hence you get the exception that you're experiencing.
It also implies that this is the only special case.
Couldn't you do something like:
for i := 0 to Qry.Params.Count - 1 do
begin
if VarType(Qry.Params[i].value) and varTypeMask = varDate then
begin
Qry.Params[i].value := Now; //or whatever you choose as your default
end
else
begin
Qry.Params[i].value := varNull;
end;
end;
What I ended up doing was this:
sNull := 'NULL';
Qry.SQL.Add(sSQL);
for i := 0 to Qry.Params.Count - 1 do begin
sParamName := Qry.Params[i].Name;
sSQL := SearchAndReplace (sSQL, ':' + sParamName, sNull, DELIMITERS);
end;
I had to write SearchAndReplace but that was easy. Delimiters are just the characters that signal the end of a word.
TmpQuery.ParamByName('MyDateTimeParam').DataType := ftDate;
TmpQuery.ParamByName('MyDateTimeParam').Clear;
TmpQuery.ParamByName('MyDateTimeParam').Bound := True;

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