FlowFields and CalcFields

Master FlowFields for computed values and CalcFields for efficient data aggregation in AL.

35 minIntermediate

Learning Objectives

Create FlowField columns with Sum, Count, and Lookup methods
Use CalcFields to compute FlowField values in code
Understand FlowFilter fields for dynamic filtering
Apply FlowFields in pages and reports

What are FlowFields?

A FlowField is a virtual field that calculates its value from data in other tables. FlowFields are not stored in the database — they're computed on demand.

Common uses:

Display total sales for a customer
Count open orders
Show inventory levels
Lookup related descriptions

Creating a FlowField

CustomerBalance.Table.al

table 50120 "Customer Balance Info"
{
    fields
    {
        field(1; "Customer No."; Code[20])
        {
            TableRelation = Customer;
        }
        field(2; "Balance (LCY)"; Decimal)
        {
            FieldClass = FlowField;
            CalcFormula = sum("Detailed Cust. Ledg. Entry"."Amount (LCY)"
                where("Customer No." = field("Customer No.")));
            Editable = false;
        }
        field(3; "No. of Orders"; Integer)
        {
            FieldClass = FlowField;
            CalcFormula = count("Sales Header"
                where("Sell-to Customer No." = field("Customer No."),
                      "Document Type" = const(Order)));
            Editable = false;
        }
    }
}

CalcFormula Methods

Method	Purpose	Example
`sum`	Total of a field	Total sales amount
`count`	Count of records	Number of open orders
`average`	Average value	Average order value
`min`	Minimum value	Earliest order date
`max`	Maximum value	Latest shipment date
`lookup`	Single field value	Item description
`exist`	Boolean check	Has open invoices?

Using CalcFields

FlowFields must be calculated before reading their value:

CalcFieldsExample.Codeunit.al

procedure ShowCustomerBalance(CustomerNo: Code[20])
var
    CustBalance: Record "Customer Balance Info";
    Balance: Decimal;
begin
    CustBalance.Get(CustomerNo);
    CustBalance.CalcFields("Balance (LCY)", "No. of Orders");

    Balance := CustBalance."Balance (LCY)";
    Message('Customer %1 has balance %2 with %3 open orders.',
        CustomerNo, Balance, CustBalance."No. of Orders");
end;

Performance

CalcFields executes a SQL query. Avoid calling it inside loops — calculate once and cache the result.

FlowFilters

FlowFilter fields provide dynamic filtering for FlowFields:

field(10; "Date Filter"; Date)
{
    FieldClass = FlowFilter;
}
field(11; "Amount This Period"; Decimal)
{
    FieldClass = FlowField;
    CalcFormula = sum("Detailed Cust. Ledg. Entry"."Amount (LCY)"
        where("Customer No." = field("Customer No."),
              "Posting Date" = field("Date Filter")));
}

Set filters in code before calculating:

Rec.SetRange("Date Filter", CalcDate('<-CM>', Today), Today);
Rec.CalcFields("Amount This Period");

FlowFields on Pages

FlowFields display automatically on pages — no special handling needed:

field("Balance (LCY)"; Rec."Balance (LCY)")
{
    ApplicationArea = All;
    ToolTip = 'Shows the calculated customer balance.';
    DrillDownPageId = "Customer Ledger Entries";
}

The DrillDownPageId property lets users click the FlowField to see underlying records.

Microsoft Pattern

Study how Microsoft uses FlowFields in standard tables like Customer, Vendor, and Item. The patterns are consistent and battle-tested.

You've completed the AL Development Fundamentals course. You now have the foundation to build real Business Central extensions. Continue with our Pages & UI course to learn how to create beautiful user interfaces.