NullStr to NULL in SQLQuery
lazarus / 16-Databases

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BSaidus · 2025-09-22 12:03

Hello.

Given this code:


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i // v_int :
TLongIntFirld// v_txtc: TStringField// v_txtt: TMemoField const  CSQL
= 'INSERT INTO uc_temp (v_int, v_txtc, v_txtt) VALUES (%d, %s,
%s);';var  LtextSQL: string;  Lf1: LongInt;  Lf2, Lf3: String;begin  
if not TryStrToInt(Edit1.Text, Lf1) then   begin    // Lf1 = Null; 
end;       Lf2 := Edit2.Text;  if Trim(Lf2) = '' then   begin    //
Lf2 = Null;    end;    Lf3 := Memo2.Text;  if Trim(Lf3) = '' then  
begin    // Lf3 = Null;        end;       LtextSQL := Format(CSQL,
[Lf1, Lf2, Lf3]);   Memo1.Append(LtextSQL);   Self.ZQuery1.SQL.Clear;
 // ...  end; 
My Question is, How to Convert Empty Value ( for string = '', for
Integer = '' ) to Null, in order to when executing
sql statement, the Empty value will be replaced by NULL.

IN my exemple, I use Edit & Memo to get input values, if they are
empty then I Format the query with NULL

  Ie:

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i    
LtextSQL := INSERT INTO uc_temp (v_int, v_txtc, v_txtt) VALUES (NULL,
NULL, NULL);  


PS: I do not want to construct the query using string concatination.

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dseligo · 2025-09-22 12:12

Use parameters.

You use them like this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i   CSQL =
'INSERT INTO uc_temp (v_int, v_txtc, v_txtt) VALUES (:v_int, :v_txtc,
:v_txtt)';...ParamByName('v_int').AsInteger :=
1;ParamByName('v_txtc').AsString := 'abc';ParamByName('txtt').AsString
:= 'cde'; 
If you want null value, you do it like this:
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i
ParamByName('v_int').Clear;

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BSaidus · 2025-09-22 12:17

Thank you.
I'll do it like that.