客户端动态条件

有两种方法：

一、首先要设置服务端的服务AllowWhereSQL为True;

客户端

with ClientDataModule.dtCustomers do begin 

    Close;
    // Prepares the custom WHERE clause
    Where.Clear;
    Where.AddConditions(['CustomerIdx','FirstName','LastName','City'],
 
                        [cEqual,cLike,cLike,cLike],
 
                        [eCode.Text,eFirstName.Text,eLastName.Text,
 
                         eCity.Text], opAnd);
     Close;
    Memo1.Text:=Where.Clause;
    if Where.Empty
      then stWhereClause.Caption := msg_NoCondition
      else stWhereClause.Caption := Where.Clause;
    MaxRecords := seMaxCustomers.Value;
    Open;
 end;

说明：
//一 复合条件
//    Where.AddConditions(['CustomerID'],
//                        [cEqual],
//                        ['ALFKI'], opAnd);
//二  增加一段条件
//    Where.AddText('CustomerID = ''ALFKI''');
//三  增加一个in条件
    Where.AddValueGroup('CustomerID',['ALFKI']);
// OpenBraket 增加一个左括号，CloseBraket增加一个右括号
//    Where.OpenBraket;
//    Where.CloseBraket;


二、首先要设置服务端的服务AllowDynamicWhere为True;

Operations between atomic expressions can be:

　　

• comparison (less, less or equal, equal, greater or equal, greater, not equal).
• likewise (like) for string types.
• arithmetic (addition, substraction, multiplication, division).
• occurrences (in) for list expressions.

The value of the expression can be changed by unary operators (minus, not).

Examples

  WHERE LastName LIKE '%in%'

begin
  with ClientDataModule.tbl_Employees do
  begin
    Close;
    DynamicWhere.Clear;
    DynamicWhere.Expression := DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewField('Employees', 'LastName'),
      DynamicWhere.NewConstant('%in%', datString), dboLike);
    Open();
  end;
end;

WHERE(LastName LIKE '%in%') OR (Not(EmployeeID = 5))

begin
  with ClientDataModule.tbl_Employees do
  begin
    Close;
    DynamicWhere.Clear;
    DynamicWhere.Expression := DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewBinaryExpression(DynamicWhere.NewField('Employees',
      'LastName'), DynamicWhere.NewConstant('%in%', datString), dboLike),
      DynamicWhere.NewUnaryExpression(DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewField('Employees', 'EmployeeID'),
      DynamicWhere.NewConstant(5, datInteger), dboEqual), duoNot), dboOr);
    Open();
  end;
end;

WHERE((LastName LIKE '%in%') OR (Not(EmployeeID = 5))) AND
  (FirstName IN ('Nancy', 'Robert'))

var
  lWhereExpression: TDAWhereExpression;

begin
  with ClientDataModule.tbl_Employees do
  begin
    Close;
    DynamicWhere.Clear;
    lWhereExpression := DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewBinaryExpression(DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewField('Employees', 'LastName'),
      DynamicWhere.NewConstant('%in%', datString), dboLike),
      DynamicWhere.NewUnaryExpression(DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewField('Employees', 'EmployeeID'),
      DynamicWhere.NewConstant(5, datInteger), dboEqual), duoNot), dboOr),
      DynamicWhere.NewBinaryExpression(DynamicWhere.NewField('Employees',
      'FirstName'), DynamicWhere.NewList([DynamicWhere.NewConstant('Robert',
      datString), DynamicWhere.NewConstant('Nancy', datString)]),
      dboIn), dboAnd);
    DynamicWhere.Expression := lWhereExpression;
    Open();
  end;
end;

WHERE(Upper(LastName)LIKE '%IN%')

begin
  with ClientDataModule.tbl_Employees do
  begin
    Close;
    DynamicWhere.Clear;
    DynamicWhere.Expression := DynamicWhere.NewBinaryExpression
      (DynamicWhere.NewMacro('UpperCase(LastName)'),
      DynamicWhere.NewConstant('%IN%', datString), dboLike);
    Open();
  end;
end;
end;