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Author 7 remedial BCQuality knowledge articles plus good/bad AL samples (21 files) covering AL master-table and data-model design: - data-modeling: master No. from number series in OnInsert; use codeunit "No. Series" not obsolete NoSeriesManagement; setup table is a singleton; set Last Date Modified in OnModify and OnRename; enforce Blocked in referencing code not in the master. - style: ApplicationArea required on page controls (AS0062). - appsource: object affixes prevent collisions (AS0011). Clean-room authored from own BC knowledge; specifics verified against public sources only (learn.microsoft.com, microsoft/BCApps). Introduces two new domains (data-modeling, appsource). Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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A setup table is a singleton: one blank-keyed row, no insert or delete
Description
An application-area setup table (Sales & Receivables Setup, Inventory Setup, and any custom * Setup) holds exactly one record per company. Its primary key is a single Code[10] field named Primary Key, and the row's value is left blank. Nothing else identifies the row — there is only ever one.
The setup card page enforces the singleton: InsertAllowed = false and DeleteAllowed = false stop a second row or an empty table, and the page guarantees the row exists on first open — typically OnOpenPage with if not Rec.Get() then begin Rec.Init(); Rec.Insert(); end;, or a GetRecordOnce helper on the table. Consuming code then reads it with a plain Get(). The read side needs no access optimization — see singleton-setup-tables-need-no-access-optimization.md.
Best Practice
Primary Key Code[10] is the sole key; the setup is surfaced through a Card page with InsertAllowed = false, DeleteAllowed = false, and an open-time guard that inserts the blank row if it is missing.
See sample: setup-table-is-a-singleton.good.al.
Anti Pattern
An Integer / AutoIncrement key, a page that allows insert or delete, or a List page over the setup table. Any of these lets the table hold zero or many rows, so "the setup" becomes ambiguous and Get() may fail or read the wrong record.
See sample: setup-table-is-a-singleton.bad.al.