PRACTICAL GUIDEUnder review

Recno queries and DbGoTo positioning

Separates the SQL cursor from the positioned real table.

Recno queries and DbGoTo positioningAdvPL

01 · OVERVIEW

Overview

A recno query selects the real table R_E_C_N_O_ under an alias, converts the numeric field when needed, and scans a read cursor. Each recno can position the real table with DbGoTo. The query neither locks nor validates a later update: recheck existence, branch, deletion and business rules before writing. This example uses an already-open caller-owned cursor with numeric A1RECNO and an open SA1, without writes. Preserve SA1 position separately when repositioning it. (Sources: refs. 1–2.)

03 · PRACTICAL EXAMPLE

Commented example

#Include "Protheus.ch"

User Function Ed609()
    // Uninvoked block; cQuery must contain numeric A1RECNO.
    Local bPosition := {|cQuery| SA1->(DbGoTo((cQuery)->A1RECNO))}
    ConOut(ValType(bPosition))
Return Nil

Expected result

Builds the positioning step without opening a query or changing a table. Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

BEST PRACTICES

During scanning, Eof and DbSkip belong to the cursor, not the positioned table; use a dynamic alias and close only your cursor.
Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

Recno queries and DbGoTo positioning

Overview

Commented example

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