1

我有一个对 QSqlQuery 的调用，当我使用 QSqlQuery::bindValue 时它不返回任何行，但是当我使用 QString::arg 添加值时确实返回行。

具体来说，这不返回任何内容：

QSqlQuery q(QSqlDatabase::database( mDbAdapter->dbFilename() ));
q.prepare("select Focus.TextFormId as ID, Focus, TextForm, Gloss from (select TextFormId,group_concat( Transcription , ' ' ) as TextForm, group_concat( Gloss , '-' ) as Gloss from (select TextFormId,AllomorphId,Allomorph.Form as Transcription,LexicalEntryGloss.Form as Gloss from MorphologicalAnalysisMembers,Allomorph,LexicalEntryGloss where TextFormId in ( select TextFormId from MorphologicalAnalysisMembers where AllomorphId in (select _id from Allomorph where  LexicalEntryId=:LexicalEntryId and WritingSystem=:TextFormWS) ) and AllomorphId = Allomorph._id and Allomorph.LexicalEntryId = LexicalEntryGloss.LexicalEntryId and LexicalEntryGloss.WritingSystem=:GlossWS order by TextFormId, AllomorphOrder) group by TextFormId ) as Concatenation left join  ( select TextFormId, Form as Focus from Allomorph,MorphologicalAnalysisMembers on Allomorph._id=MorphologicalAnalysisMembers.AllomorphId and LexicalEntryId=:LexicalEntryId ) as Focus on Focus.TextFormId = Concatenation.TextFormId;");
q.bindValue(":LexicalEntryId", mLexicalEntryId);
q.bindValue(":GlossWS", mGlossWs.id());
q.bindValue(":TextFormWS", mTextFormWs.id());
if( !q.exec() )
    qWarning() << q.lastError().text() << q.executedQuery();

而这会返回正确的结果

QSqlQuery q(QSqlDatabase::database( mDbAdapter->dbFilename() ));
q.prepare(
        QString("select Focus.TextFormId as ID, Focus, TextForm, Gloss from (select TextFormId,group_concat( Transcription , ' ' ) as TextForm, group_concat( Gloss , '-' ) as Gloss from (select TextFormId,AllomorphId,Allomorph.Form as Transcription,LexicalEntryGloss.Form as Gloss from MorphologicalAnalysisMembers,Allomorph,LexicalEntryGloss where TextFormId in ( select TextFormId from MorphologicalAnalysisMembers where AllomorphId in (select _id from Allomorph where  LexicalEntryId=%1 and WritingSystem=%3) ) and AllomorphId = Allomorph._id and Allomorph.LexicalEntryId = LexicalEntryGloss.LexicalEntryId and LexicalEntryGloss.WritingSystem=%2 order by TextFormId, AllomorphOrder) group by TextFormId ) as Concatenation left join  ( select TextFormId, Form as Focus from Allomorph,MorphologicalAnalysisMembers on Allomorph._id=MorphologicalAnalysisMembers.AllomorphId and LexicalEntryId=%1 ) as Focus on Focus.TextFormId = Concatenation.TextFormId;")
        .arg(mLexicalEntryId).arg(mGlossWs.id()).arg(mTextFormWs.id())
        );
if( !q.exec() )
    qWarning() << q.lastError().text() << q.executedQuery();

重现整个数据库会有点麻烦，但这里的查询形式更易于理解：

select Focus.TextFormId as ID, Focus, TextForm, Gloss from (select TextFormId,group_concat( Transcription , ' ' ) as TextForm, group_concat( Gloss , '-' ) as Gloss
from 
(select TextFormId,AllomorphId,Allomorph.Form as Transcription,LexicalEntryGloss.Form as Gloss 
    from MorphologicalAnalysisMembers,Allomorph,LexicalEntryGloss 
    where TextFormId in 
        ( select TextFormId from MorphologicalAnalysisMembers where AllomorphId in 
            (select _id from Allomorph where  LexicalEntryId=%1 and WritingSystem=%3) ) 
        and AllomorphId = Allomorph._id 
        and Allomorph.LexicalEntryId = LexicalEntryGloss.LexicalEntryId 
        and LexicalEntryGloss.WritingSystem=%2 
        order by TextFormId, AllomorphOrder) 
    group by TextFormId ) as Concatenation 
    left join  
    ( select TextFormId, Form as Focus from Allomorph,MorphologicalAnalysisMembers 
        on Allomorph._id=MorphologicalAnalysisMembers.AllomorphId and LexicalEntryId=%1 ) 
    as Focus on Focus.TextFormId = Concatenation.TextFormId;

考虑到可能有改进查询的方法，我搜索了文档并找不到任何表明 QSqlQuery::bindValue 有限制的迹象。

4

1 回答 1

1

通过更改绑定值的方式，我最终能够使其与绑定一起使用。如果我mLexicalEntryId使用不同的占位符（下面的第一个示例）插入两次，或者我使用 ? 绑定值的表示法（下面的第二个示例）。虽然我更喜欢使用占位符，但为同一个变量设置两个不同的占位符感觉很愚蠢，所以我会坚持使用 ? 符号。

q.prepare("select Focus.TextFormId as ID, Focus, TextForm, Gloss from (select TextFormId,group_concat( Transcription , ' ' ) as TextForm, group_concat( Gloss , '-' ) as Gloss from (select TextFormId,AllomorphId,Allomorph.Form as Transcription,LexicalEntryGloss.Form as Gloss from MorphologicalAnalysisMembers,Allomorph,LexicalEntryGloss where TextFormId in ( select TextFormId from MorphologicalAnalysisMembers where AllomorphId in (select _id from Allomorph where  LexicalEntryId=:One and WritingSystem=:Three) ) and AllomorphId = Allomorph._id and Allomorph.LexicalEntryId = LexicalEntryGloss.LexicalEntryId and LexicalEntryGloss.WritingSystem=:Two order by TextFormId, AllomorphOrder) group by TextFormId ) as Concatenation left join  ( select TextFormId, Form as Focus from Allomorph,MorphologicalAnalysisMembers on Allomorph._id=MorphologicalAnalysisMembers.AllomorphId and LexicalEntryId=:Four ) as Focus on Focus.TextFormId = Concatenation.TextFormId;");
q.bindValue(":One", mLexicalEntryId);
q.bindValue(":Two", mGlossWs.id());
q.bindValue(":Three", mTextFormWs.id());
q.bindValue(":Four", mLexicalEntryId);

q.prepare("select Focus.TextFormId as ID, Focus, TextForm, Gloss from (select TextFormId,group_concat( Transcription , ' ' ) as TextForm, group_concat( Gloss , '-' ) as Gloss from (select TextFormId,AllomorphId,Allomorph.Form as Transcription,LexicalEntryGloss.Form as Gloss from MorphologicalAnalysisMembers,Allomorph,LexicalEntryGloss where TextFormId in ( select TextFormId from MorphologicalAnalysisMembers where AllomorphId in (select _id from Allomorph where  LexicalEntryId=? and WritingSystem=?) ) and AllomorphId = Allomorph._id and Allomorph.LexicalEntryId = LexicalEntryGloss.LexicalEntryId and LexicalEntryGloss.WritingSystem=? order by TextFormId, AllomorphOrder) group by TextFormId ) as Concatenation left join  ( select TextFormId, Form as Focus from Allomorph,MorphologicalAnalysisMembers on Allomorph._id=MorphologicalAnalysisMembers.AllomorphId and LexicalEntryId=? ) as Focus on Focus.TextFormId = Concatenation.TextFormId;");
q.addBindValue(mLexicalEntryId);
q.addBindValue(mTextFormWs.id());
q.addBindValue(mGlossWs.id());
q.addBindValue(mLexicalEntryId);
于 2013-02-06T09:08:34.070 回答