Delphi Tstringlist，将字符串作为带引号的逗号分隔字符串获取？

Question

I have a Tstringlist containing a list of keys used in a database table. I'd like a simple way to generate one string containing all the keys, with each separated by a comma and enclosed in single quotes. This is so that it can be used in a SQL 'IN' statement eg WHERE FieldX IN ('One','Two','Three') .

I've tried using quotechar but it is ignored when reading the commatext. eg the following code

procedure junk;
var
  SL : Tstringlist;
  s : string;
begin
 SL := Tstringlist.Create;
 SL.Delimiter :=','; //comma delimiter
 SL.QuoteChar := ''''; //single quote around strings
 SL.Add('One');
 SL.Add('Two');
 SL.Add('Three');
 try
   s :=  SL.commatext;
   showmessage(s);
 finally
   SL.Free;
 end; //finally
end; //junk

shows the message One,Two,Three - without any quotes.

I know I can do it the long way round, as in

procedure junk;
var
  SL : Tstringlist;
  s : string;
  i : integer;
begin
 SL := Tstringlist.Create;
 SL.Delimiter :=','; //comma delimiter
 SL.Add('One');
 SL.Add('Two');
 SL.Add('Three');
 try
 s := '';
 for I := 0 to SL.Count - 1 do
    begin
    s := s +  ',' + '''' + SL[i] + '''';
    end;
 delete(s,1,1);
 showmessage(s);
 finally
   SL.Free;
 end;//finally
end;

but is there a simpler way using properties of the Tstringlist itself?

Answer 1

Use sl.DelimitedText instead of sl.CommaText to make it follow your settings. CommaText will temporarily change the Delimiter and QuoteChar to some hardcoded values.

Answer 2

If you're using D2006 or later, you can use a CLASS HELPER:

USES Classes,StrUtils;

TYPE
  TStringListHelper = CLASS HELPER FOR TStrings
                        FUNCTION ToSQL : STRING;
                      END;

FUNCTION TStringListHelper.ToSQL : STRING;
  VAR
    S : STRING;

  FUNCTION QuotedStr(CONST S : STRING) : STRING;
    BEGIN
      Result:=''''+ReplaceStr(S,'''','''''')+''''
    END;

  BEGIN
    Result:='';
    FOR S IN Self DO BEGIN
      IF Result='' THEN Result:='(' ELSE Result:=Result+',';
      Result:=Result+QuotedStr(S)
    END;
    IF Result<>'' THEN Result:=Result+')'
  END;

This code:

SL:=TStringList.Create;
SL.Add('One');
SL.Add('Two');
SL.Add('Number Three');
SL.Add('It''s number 4');
WRITELN('SELECT * FROM TABLE WHERE FIELD IN '+SL.ToSQL);

will then output:

SELECT * FROM TABLE WHERE FIELD IN ('One','Two','Number Three','It''s number 4')

Answer 3

CommaText (and apparently also DelimitedText) can not be relied on to add the quotes, because they treat single word and multi word strings differently.

When retrieving CommaText, any string in the list that include spaces, commas or quotes will be contained in double quotes, and any double quotes in a string will be repeated.

There doesn't seem to be any combination with the TStringList alone, so I suggest you add the strings using QuotedStr . Following settings work as you wish, regardless of, whether strings are single words or multi words:

 SL := Tstringlist.Create;
 SL.Delimiter :=','; //comma delimiter
 SL.StrictDelimiter := True;
// SL.QuoteChar := ''''; //single quote around strings
// SL.Add('One');
// SL.Add('Two words');
// SL.Add('Three');
 SL.Add(QuotedStr('One'));
 SL.Add(QuotedStr('Two words'));
 SL.Add(QuotedStr('Three'));
 s := SL.CommaText; // or SL.DelimitedText;
 showmessage(s);

Output is:

'One','Two words','Three'

Answer 4

The TStrings.DelimitedText methods quote only the strings when needed: when there's something link O'ne this will print as 'O''ne' - ie it double the quotes.

You can achieve what you want setting a convenience delimiter and the QuoteChar property to the #0 value and then replacing the delimiters with the quotes.

procedure junk;
var
  sl : Tstringlist;
  s: string;
begin
  sl := Tstringlist.Create;
  try
    sl.Delimiter := '|';
    sl.QuoteChar := #0;//no quote
    sl.Add('On''e');
    sl.Add('Two');
    sl.Add('Three');

    //escape the single quotes
    s := StringReplace(sl.DelimitedText, '''', '''''', [rfReplaceAll]);

    //replace the delimiters and quote the text
    s := '''' +  StringReplace(s, sl.Delimiter, ''',''', [rfReplaceAll]) + '''';

    WriteLn(s);

  finally
    sl.Free;
  end;
end;

Answer 5

我已经解决了类似的问题：

  s := ''' + StringReplace(sl.CommaText, ',', ''',''', [rfReplaceAll]) + '''