Merge branch 'master' of https://github.com/Steema/TeeGrid-VCL-FMX-Samples

Author: davidberneda

demos/FireMonkey/Database/Master_Detail_FireDAC/readme.md

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+## Master-Detail example using FireDAC datasets
+
+This demo shows how to create 3 levels of nested sub-grid rows.
+
+![](https://raw.github.com/Steema/TeeGrid-VCL-FMX-Samples/master/docs/img/TeeGrid_Three_Level_SubGrids_FireDAC.png)
+
+Adding a sub-grid to another sub-grid is done in the following steps:
+
+- Create a new "Expander" render
+
+  This is the class that draws the "+" and "-" symbols you can click to expand or collapse a row.
+
+  For the main grid:
+
+  ```delphi
+  uses Tee.Renders;
+  var Expander : TExpanderRender;
+  Expander:=TeeGrid1.Grid.Current.NewExpander;
+  ```
+
+  For any sub-grid, you should do the same as above but using the "NewGroup" variable that is passed when a sub-grid is expanded:
+
+  ```delphi
+  procedure TMasterDetail.DetailNewGroup(const Sender,NewGroup:TRowGroup);
+  begin
+    Expander:=NewGroup.NewExpander;
+  ...
+  ```
+  
+  
+- The Expander should be connected to an event that will give the detail data rows we want for a given master row:
+
+  ```delphi
+  procedure TMasterDetail.GetOrders(const Sender: TExpanderRender; const ARow:Integer; out AData:TObject);
+  begin
+    // Return a new Data using a clone of Orders rows for a given Customer
+    AData:=TVirtualDBData.From(SampleData.OrdersOfCustomer(ARow+1));
+
+    // Data should be destroyed automatically
+    TVirtualDBData(AData).OwnsData:=True;
+  end;
+
+  Expander.OnGetData:=GetOrders;
+  ```
+
+- In this example, the "OrdersOfCustomer" function is done manually using FireDAC TFDQuery components:
+
+  ```delphi
+  function TSampleData.OrdersOfCustomer(const ARecNo:Integer):TDataSet;
+
+    // Return the CustomerID for row: ARow
+    function CustomerID:String;
+    begin
+      CustomersTable.RecNo:=ARecNo;
+      result:=CustomersTable.FieldByName('CustomerID').AsString;
+    end;
+
+    // Execute OrdersTable query for a given CustomerID
+    procedure FilterOrders(const ACustomerID:String);
+    begin
+      OrdersTable.Close;
+      OrdersTable.ParamByName('Cust').AsString:=ACustomerID;
+      OrdersTable.Open;
+    end;
+
+  begin
+    FilterOrders(CustomerID);
+    result:=CloneData(OrdersTable);
+  end;
+  ```
+
+  You can obtain the sub-details rows the way you like.
+
+  If you use [TeeBI Datamining Library](https://github.com/Steema/TeeBI) these steps are much more simplified because TeeBI knows the relationship master-detail between datasets and prepares data automatically.
+  There is a TeeBI and TeeGrid example showing these levels of sub-grid details:
+
+  [TeeBI and TeeGrid Example](https://github.com/Steema/TeeGrid-VCL-FMX-Samples/tree/master/demos/VCL/TeeBI)
+  
+