qsqlquery.cpp

奇趣公司比较新的qt/emd版本

    of the fields in the query is undefined.

    An invalid QVariant is returned if field \a index does not
    exist, if the query is inactive, or if the query is positioned on
    an invalid record.

    \sa previous() next() first() last() seek() isActive() isValid()
*/

QVariant QSqlQuery::value(int index) const
{
    if (isActive() && isValid() && (index > QSql::BeforeFirstRow))
        return d->sqlResult->data(index);
    qWarning("QSqlQuery::value: not positioned on a valid record");
    return QVariant();
}

/*!
    Returns the current internal position of the query. The first
    record is at position zero. If the position is invalid, the
    function returns QSql::BeforeFirstRow or
    QSql::AfterLastRow, which are special negative values.

    \sa previous() next() first() last() seek() isActive() isValid()
*/

int QSqlQuery::at() const
{
    return d->sqlResult->at();
}

/*!
    Returns the text of the current query being used, or an empty
    string if there is no current query text.

    \sa executedQuery()
*/

QString QSqlQuery::lastQuery() const
{
    return d->sqlResult->lastQuery();
}

/*!
    Returns the database driver associated with the query.
*/

const QSqlDriver *QSqlQuery::driver() const
{
    return d->sqlResult->driver();
}

/*!
    Returns the result associated with the query.
*/

const QSqlResult* QSqlQuery::result() const
{
    return d->sqlResult;
}

/*!
    Retrieves the record at position \a index, if available, and
    positions the query on the retrieved record. The first record is
    at position 0. Note that the query must be in an active state and
    isSelect() must return true before calling this function.

    If \a relative is false (the default), the following rules apply:

    \list
    \o If \a index is negative, the result is positioned before the
    first record and false is returned.
    \o Otherwise, an attempt is made to move to the record at position
    \a index. If the record at position \a index could not be retrieved, the
    result is positioned after the last record and false is returned. If
    the record is successfully retrieved, true is returned.
    \endlist

    If \a relative is true, the following rules apply:

    \list
    \o If the result is currently positioned before the first
    record or on the first record, and \a index is negative, there is no
    change, and false is returned.
    \o If the result is currently located after the last record, and
    \a index is positive, there is no change, and false is returned.
    \o If the result is currently located somewhere in the middle,
    and the relative offset \a index moves the result below zero, the
    result is positioned before the first record and false is
    returned.
    \o Otherwise, an attempt is made to move to the record \a index
    records ahead of the current record (or \a index records behind the
    current record if \a index is negative). If the record at offset \a index
    could not be retrieved, the result is positioned after the last
    record if \a index >= 0, (or before the first record if \a index is
    negative), and false is returned. If the record is successfully
    retrieved, true is returned.
    \endlist

    \sa next() previous() first() last() at() isActive() isValid()
*/
bool QSqlQuery::seek(int index, bool relative)
{
    if (!isSelect() || !isActive())
        return false;
    int actualIdx;
    if (!relative) { // arbitrary seek
        if (index < 0) {
            d->sqlResult->setAt(QSql::BeforeFirstRow);
            return false;
        }
        actualIdx = index;
    } else {
        switch (at()) { // relative seek
        case QSql::BeforeFirstRow:
            if (index > 0)
                actualIdx = index;
            else {
                return false;
            }
            break;
        case QSql::AfterLastRow:
            if (index < 0) {
                d->sqlResult->fetchLast();
                actualIdx = at() + index;
            } else {
                return false;
            }
            break;
        default:
            if ((at() + index) < 0) {
                d->sqlResult->setAt(QSql::BeforeFirstRow);
                return false;
            }
            actualIdx = at() + index;
            break;
        }
    }
    // let drivers optimize
    if (isForwardOnly() && actualIdx < at()) {
        qWarning("QSqlQuery::seek: cannot seek backwards in a forward only query");
        return false;
    }
    if (actualIdx == (at() + 1) && at() != QSql::BeforeFirstRow) {
        if (!d->sqlResult->fetchNext()) {
            d->sqlResult->setAt(QSql::AfterLastRow);
            return false;
        }
        return true;
    }
    if (actualIdx == (at() - 1)) {
        if (!d->sqlResult->fetchPrevious()) {
            d->sqlResult->setAt(QSql::BeforeFirstRow);
            return false;
        }
        return true;
    }
    if (!d->sqlResult->fetch(actualIdx)) {
        d->sqlResult->setAt(QSql::AfterLastRow);
        return false;
    }
    return true;
}

/*!
    Retrieves the next record in the result, if available, and
    positions the query on the retrieved record. Note that the result
    must be in an active state and isSelect() must return true before
    calling this function or it will do nothing and return false.

    The following rules apply:

    \list
    \o If the result is currently located before the first
    record, e.g. immediately after a query is executed, an attempt is
    made to retrieve the first record.

    \o If the result is currently located after the last record,
    there is no change and false is returned.

    \o If the result is located somewhere in the middle, an attempt
    is made to retrieve the next record.
    \endlist

    If the record could not be retrieved, the result is positioned after
    the last record and false is returned. If the record is successfully
    retrieved, true is returned.

    \sa previous() first() last() seek() at() isActive() isValid()
*/

bool QSqlQuery::next()
{
    if (!isSelect() || !isActive())
        return false;
    bool b = false;
    switch (at()) {
    case QSql::BeforeFirstRow:
        b = d->sqlResult->fetchFirst();
        return b;
    case QSql::AfterLastRow:
        return false;
    default:
        if (!d->sqlResult->fetchNext()) {
            d->sqlResult->setAt(QSql::AfterLastRow);
            return false;
        }
        return true;
    }
}

/*!
    Retrieves the previous record in the result, if available, and
    positions the query on the retrieved record. Note that the result
    must be in an active state and isSelect() must return true before
    calling this function or it will do nothing and return false.

    The following rules apply:

    \list
    \o If the result is currently located before the first record,
    there is no change and false is returned.

    \o If the result is currently located after the last record, an
    attempt is made to retrieve the last record.

    \o If the result is somewhere in the middle, an attempt is made
    to retrieve the previous record.
    \endlist

    If the record could not be retrieved, the result is positioned
    before the first record and false is returned. If the record is
    successfully retrieved, true is returned.

    \sa next() first() last() seek() at() isActive() isValid()
*/

bool QSqlQuery::previous()
{
    if (!isSelect() || !isActive())
        return false;
    if (isForwardOnly()) {
        qWarning("QSqlQuery::seek: cannot seek backwards in a forward only query");
        return false;
    }

    bool b = false;
    switch (at()) {
    case QSql::BeforeFirstRow:
        return false;
    case QSql::AfterLastRow:
        b = d->sqlResult->fetchLast();
        return b;
    default:
        if (!d->sqlResult->fetchPrevious()) {
            d->sqlResult->setAt(QSql::BeforeFirstRow);
            return false;
        }
        return true;
    }
}

/*!
    Retrieves the first record in the result, if available, and
    positions the query on the retrieved record. Note that the result
    must be in an active state and isSelect() must return true before
    calling this function or it will do nothing and return false.
    Returns true if successful. If unsuccessful the query position is
    set to an invalid position and false is returned.

    \sa next() previous() last() seek() at() isActive() isValid()
*/

bool QSqlQuery::first()
{
    if (!isSelect() || !isActive())
        return false;
    if (isForwardOnly() && at() > QSql::BeforeFirstRow) {
        qWarning("QSqlQuery::seek: cannot seek backwards in a forward only query");
        return false;
    }
    bool b = false;
    b = d->sqlResult->fetchFirst();
    return b;
}

/*!
    Retrieves the last record in the result, if available, and
    positions the query on the retrieved record. Note that the result
    must be in an active state and isSelect() must return true before
    calling this function or it will do nothing and return false.
    Returns true if successful. If unsuccessful the query position is
    set to an invalid position and false is returned.

    \sa next() previous() first() seek() at() isActive() isValid()
*/

bool QSqlQuery::last()
{
    if (!isSelect() || !isActive())
        return false;
    bool b = false;
    b = d->sqlResult->fetchLast();
    return b;
}

/*!
    Returns the size of the result (number of rows returned), or -1
    if the size cannot be determined or if the database does not
    support reporting information about query sizes. Note that for
    non-\c SELECT statements (isSelect() returns false), size() will
    return -1. If the query is not active (isActive() returns false),
    -1 is returned.

    To determine the number of rows affected by a non-\c SELECT
    statement, use numRowsAffected().

    \sa isActive() numRowsAffected() QSqlDriver::hasFeature()
*/
int QSqlQuery::size() const
{
    if (isActive() && d->sqlResult->driver()->hasFeature(QSqlDriver::QuerySize))
        return d->sqlResult->size();
    return -1;
}

/*!
    Returns the number of rows affected by the result's SQL statement,
    or -1 if it cannot be determined. Note that for \c SELECT
    statements, the value is undefined; use size() instead. If the
    query is not active (isActive() returns false), -1 is returned.

    \sa size() QSqlDriver::hasFeature()
*/

int QSqlQuery::numRowsAffected() const
{
    if (isActive())
        return d->sqlResult->numRowsAffected();
    return -1;
}

/*!
    Returns error information about the last error (if any) that
    occurred with this query.

    \sa QSqlError, QSqlDatabase::lastError()
*/

QSqlError QSqlQuery::lastError() const
{
    return d->sqlResult->lastError();
}

/*!
    Returns true if the query is currently positioned on a valid
    record; otherwise returns false.
*/

bool QSqlQuery::isValid() const
{
    return d->sqlResult->isValid();
}

/*!
    Returns true if the query is currently active; otherwise returns
    false.
*/

bool QSqlQuery::isActive() const
{
    return d->sqlResult->isActive();
}

/*!
    Returns true if the current query is a \c SELECT statement;
    otherwise returns false.
*/

bool QSqlQuery::isSelect() const
{
    return d->sqlResult->isSelect();
}

/*!
    Returns true if you can only scroll forward through a result set;
    otherwise returns false.

    \sa setForwardOnly(), next()
*/
bool QSqlQuery::isForwardOnly() const
{
    return d->sqlResult->isForwardOnly();
}