论述-Sqlite3 开发优化

1. 使用事务，将多条数据库更改语句或者，循环遍历语句放到一次事务中来处理。

     SqliteDB::startTransaction()；

         do_CRUD;

         MayBe: SqliteDB::RollBack();

     SqliteDB::Commit();

2. 使用批处理执行参数为集合类型的操作

   QVariantList    bindValue1;

  QVariantList     bindValue2;

 QString   strSql = " delete from tablename where  field1 = ? and field2 = ?"

  QSqlquery sqlQuery.addbindValue(bindValue1);

  QSqlquery sqlQuery.addbindValue(bindValue2);

     sqlQuery.queryBatch();

      getResult();

3. 一般对于插入操作，要返回插入数据库后，所在行的自增长序号ID, 或者自定义的某一列。后续流程会用到这个ID，来标记数据行。

        两种方式获取插入自增长ID：

    -select last_insert_rowid() as newID from TableName

    select max(ID) from 表

    还可以放在事务一起处理。

注意的是：

SQLiteAPI 函数sqlite3_last_insert_rowid()可以取得最后一条插入的记录的rowid。但sqlite3_last_insert_rowid()是基于当前进程的。也就是说，sqlite3_last_insert_rowid()取到的是当前进程最后一次插入记录的rowid。对于不是当前进程插入的记录，sqlite3_last_insert_rowi()均返回0。sqlite3_last_insert_rowi()对应的SQL声明为last_insert_rowid()，

    

操作例子：

bool SampleRecordDAO::updatePrintStatus(const QSet<int> &sampleIdSet, bool isPrint)
{
    int sampleIdSize = sampleIdSet.size();
    if (sampleIdSize <= 0)
    {
        return true;
    }

    QSqlQuery query(SqliteDbHelper::Instance()->getDB());
    query.prepare("UPDATE SampleInfo SET ResultStatePrint = ? where ID = ? ");
    QVariantList stateList,idList;
    for (QSet<int>::const_iterator idItr = sampleIdSet.begin(); idItr != sampleIdSet.end(); ++idItr)
    {
        stateList << (int)isPrint;
        idList << *idItr;
    }
    query.addBindValue(stateList);
    query.addBindValue(idList);
    if (!query.execBatch())
    {
        revDebug << query.lastError().text();
        return false;
    }
    return true;
}

bool SampleRecordDAO::deleteSampleInfoAbout4Ids(QList<int> sampleIds)
{
    //1.Haven't Sample Id
    int sampleSize = sampleIds.size();
    if (sampleSize <= 0)
    {
        return true;
    }
    //2.Build Sample Id List
    QVariantList idList;
    for (int sampleIdx = 0; sampleIdx < sampleSize; ++sampleIdx)
    {
        idList << sampleIds.at(sampleIdx);
    }
    //3.Delete DB
    SqliteDbHelper::Instance()->startTransaction();
    QSqlQuery query(SqliteDbHelper::Instance()->getDB());
    do
    {
        query.prepare("DELETE FROM SampleInfo WHERE ID = ? ");
        query.addBindValue(idList);
        if (!query.execBatch())
        {
            break;
        }

        query.prepare("DELETE FROM SampleInfoOrg WHERE ID = ? ");
        query.addBindValue(idList);
        if (!query.execBatch())
        {
            break;
        }

        query.prepare("DELETE FROM MicroscopyInfoTable WHERE ID = ? ");
        query.addBindValue(idList);
        if (!query.execBatch())
        {
            break;
        }

        query.prepare("DELETE FROM SampleInforgraincountTable WHERE ID = ? ");
        query.addBindValue(idList);
        if (!query.execBatch())
        {
            break;
        }
        SqliteDbHelper::Instance()->commit();
        return true;
    }
    while(false);
    revDebug << query.lastError().text();
    SqliteDbHelper::Instance()->rollback();
    return false;
}