PRACTICAL GUIDEUnder review

ChangeQuery and database compatibility

Adapts query syntax before opening it through DBAccess.

ChangeQuery and database compatibilityAdvPL

01 · OVERVIEW

Overview

ChangeQuery(cQuery) returns SQL text adapted to the current database without opening a cursor or executing the query. Documentation requires ANSI syntax, recommends WHERE and describes parser limits: it does not guarantee compatibility for every database-native function. The community TCGenQry.PRW transforms text before TCGenQry/DbUseArea; that example does not explicitly constrain branch, so it must not be copied as an access policy. The editorial example uses a fictional table and only measures returned text. For actual queries, review RetSqlName, branch and logical-deletion filters and bound parameters. (TOTVS, n.d., ref. 1; EURAI, n.d., ref. 2)

03 · PRACTICAL EXAMPLE

Commented example

#Include "Protheus.ch"
User Function Ed299()
    Local cSql := "SELECT CODIGO FROM LIVROS WHERE 1 = 1"
    Local cAdapted
    // Fictional table; no query is opened.
    cAdapted := ChangeQuery(cSql)
    ConOut(cValToChar(Len(cAdapted)))
Return Nil

Expected result

Length depends on parser and database; there is no record set or fixed numeric result. Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

BEST PRACTICES

Do not use ChangeQuery as input sanitization or authorization. Test the query and plan on supported target databases.
Under review: editorial example neither compiled nor run in Protheus. Check includes, release, RDD and context before testing.

ChangeQuery and database compatibility

Overview

Commented example

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