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i am trying to create a function that will verify users before allowing them to login. The userID, Password and Name are stored in a data-base (MS Access). The function takes the ID, Password and Name that the user has entered and compares it to that found in the database. However when trying to find the users information through a SQL query the following error occurs: 'Parameter Brent has no default value' Brent is the user name entered by the user by means of selecting it from a drop-down menu (as to avoid spelling errors etc. the Delphi code follows:

function check (Name, ID, Password : string) : string;
  myLoop : integer;
  myField : string;
  form1.ADOQuery1.Active := false;
  form1.ADOQuery1.SQL.Text := 'SELECT [employee ID], Password, Name FROM Employees WHERE Name = ' + name;
  form1.ADOQuery1.Active := true;

  {for myLoop := 1 to 3 do
  myField := form1.DataSource1.DataSet.Fields[myLoop].AsString;
  unit1.arrEmployee[myLoop] := myField;

  if (arrEmployee[1] = ID) AND (arrEmployee[2] = Password) AND (arrEmployee[3] = Name) then
  showmessage('all your information is correct') else
  showmessage('your information is not all correct');  }  

1 solution

The error occurred maybe because you have record(s)that the Name field of theme are Null , add and null check to end of your query :

SELECT [employee ID], Password, Name FROM Employees WHERE Name = ' + name + ' AND Name IS Not Null';

Why you check the login this way ? you can easily do all login checks usign T-SQL query like :

form1.ADOQuery1.Active := False;
form1.ADOQuery1.SQL.Text := 'SELECT [employee ID], Password, Name FROM Employees                                                  WHERE Name = ' + name + ' AND Password = ' + Password + ' AND[employee ID] =' + ID;
form1.ADOQuery1.Active := True;

if (form1.ADOQuery1.RecordCount > 0) then
  // Login
  // Login failed
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