AL Data Types and Methods

Why Data Types Are Critical in AL

AL is a strongly typed ERP language. Every variable, parameter, and field must have a clearly defined data type. This is not a technical limitation—it is a business safeguard.

In Business Central, data types protect:

• Financial accuracy
• Inventory precision
• Posting correctness
• Auditability

Choosing the wrong data type is not just a coding error; it is a business risk.

Classification of AL Data Types

AL data types can be grouped into six major categories:

1. Numeric data types
2. Text and identifier data types
3. Date and time data types
4. ERP-specific complex data types
5. Object reference data types
6. System and utility data types

Each category serves a distinct role in ERP development.

Integer

The Integer data type stores whole numbers and is commonly used for counters, indexing, and control logic.

var
    LineNo: Integer;
begin
    LineNo := 10000;
end;
    

Integers should not be used for monetary or quantity values.

Decimal

The Decimal data type is used for amounts, prices, quantities, and costs. It supports precision and rounding logic required in ERP systems.

var
    UnitCost: Decimal;
    Quantity: Decimal;
    TotalCost: Decimal;
begin
    UnitCost := 45.75;
    Quantity := 10;
    TotalCost := UnitCost * Quantity;
end;
    

In Business Central, almost all financial and inventory calculations use Decimal.

BigInteger

BigInteger is used when values exceed the range of a standard Integer, such as large counters or technical identifiers.

var
    LargeCounter: BigInteger;
    

This type is rarely used in functional business logic.

Text

Text is used for descriptions, comments, and free-form input.

var
    CommentText: Text[250];
begin
    CommentText := 'Production order completed successfully';
end;
    

Text fields have a fixed maximum length.

Code

Code is used for identifiers such as customer numbers, item numbers, and document numbers.

var
    ItemNo: Code[20];
begin
    ItemNo := 'ITEM-1001';
end;
    

Although similar to Text, Code is optimized for indexing and searching and should always be used for keys and identifiers.

Char

Char stores a single character and is rarely used in business logic.

var
    Initial: Char;
begin
    Initial := 'A';
end;
    

Date

Stores calendar dates and is used heavily in posting, reporting, and period control.

var
    PostingDate: Date;
begin
    PostingDate := Today();
end;
    

Time

Stores time values without a date component.

var
    StartTime: Time;
begin
    StartTime := Time();
end;
    

DateTime

Combines date and time and is typically used for logging, integration, and background processing.

var
    CreatedAt: DateTime;
begin
    CreatedAt := CurrentDateTime();
end;
    

Duration

Represents time intervals and is used for performance measurement or scheduling.

var
    ProcessingTime: Duration;
    

These data types make AL ERP-aware.

Record

The Record data type represents a table and allows interaction with stored business data.

var
    CustomerRec: Record Customer;
begin
    CustomerRec.Get('CUST-1000');
end;
    

Records are the most important data type in AL development.

RecordRef and FieldRef

These are dynamic record and field references used for generic logic, utilities, or frameworks.

var
    RecRef: RecordRef;
    FldRef: FieldRef;
    

They are powerful but should be used carefully.

Enum

Enums represent predefined, controlled values such as statuses or types.

var
    Status: Enum "Sales Document Status";
begin
    Status := Status::Released;
end;
    

Enums prevent invalid values and improve readability.

Option (Legacy)

Options are an older construct replaced by Enums. They exist mainly in legacy code.

OptionValue: Option Open,Released,Closed;
    

New development should always use Enums instead.

Page

Used to interact with or run pages programmatically.

var
    CustomerPage: Page "Customer Card";
begin
    CustomerPage.Run();
end;
    

Codeunit

Used to call reusable business logic.

var
    PriceCalc: Codeunit "Sales Price Calc. Mgt.";
begin
    PriceCalc.Run();
end;
    

Report

Used to run reports or batch processes.

Report.Run(Report::"Customer - List");
    

Query

Used for optimized data retrieval.

var
    MyQuery: Query "Item Sales Query";
    

Boolean

Represents true or false values.

var
    IsBlocked: Boolean;
begin
    IsBlocked := false;
end;
    

Guid

Used for unique identifiers, especially in integrations.

var
    UniqueId: Guid;
begin
    UniqueId := CreateGuid();
end;
    

JsonObject, JsonArray, JsonToken

Used for integrations and API communication.

var
    JsonObj: JsonObject;
begin
    JsonObj.Add('Status', 'Success');
end;
    

HttpClient, HttpRequestMessage, HttpResponseMessage

Used for calling external services.

var
    Client: HttpClient;
    Response: HttpResponseMessage;
    

Methods in AL

Methods in AL are procedures and functions that execute logic. They can:

• Accept parameters
• Return values
• Operate on records
• Trigger validations

procedure CalculateTax(Amount: Decimal): Decimal
var
    Tax: Decimal;
begin
    Tax := Amount * 0.18;
    exit(Tax);
end;
    

//Records expose built-in methods: 
ItemRec.Validate("Unit Price", 200);
ItemRec.Modify();
    

Validation ensures standard business rules are applied.

AL does not allow unrestricted execution. All methods run within Business Central’s framework, ensuring:

• Data integrity
• Posting accuracy
• Upgrade safety

Developers extend behavior; they do not bypass it.

Common Beginner Mistakes

• Using Text instead of Code
• Using Integer for amounts
• Skipping Validate
• Overusing RecordRef
• Mixing UI and business logic

Avoiding these mistakes early leads to stable extensions.

Summary

Data types define what kind of business data AL handles, and methods define how that data is processed. Together, they form the foundation of all AL development in Business Central.

A deep understanding of data types and methods is essential for writing correct, maintainable, and ERP-aligned AL code.