PRACTICAL GUIDEUnder review

Indexes, orders and lookups in Protheus tables

Checks the order expression before building a lookup key.

Indexes, orders and lookups in Protheus tablesAdvPL

01 · OVERVIEW

Overview

DBSetOrder selects an open area’s logical order and may fail for nonexistent orders. IndexKey returns its expression as text without creating/rebuilding indexes. DBSeek requires a compatible order, key type and composition; check its Boolean result before reading fields. With lSoftSeek true, approximate positioning may occur even when the return is false: position does not prove a match. This sample only inspects SB1’s current order rather than assuming order number, width or code. SQL ORDER BY and physical index selection are separate issues. (Sources: refs. 1–4.)

03 · PRACTICAL EXAMPLE

Commented example

#Include "Protheus.ch"

User Function Ed738()
    Local cExpression := ""
    // Inspect an existing alias without changing order or position.
    If Select("SB1") > 0
        cExpression := SB1->(IndexKey())
    EndIf
    ConOut(cExpression)
Return Nil

Expected result

Displays the current expression or an empty string; does not look up a product. Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

BEST PRACTICES

Do not trim fixed-width key components. Preserve area/order if processing changes them; do not apply the technical sample’s table-creation routine to standard tables.
Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

Indexes, orders and lookups in Protheus tables

Overview

Commented example

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