qsqlquery.cpp

奇趣公司比较新的qt/emd版本

/*!
    Sets forward only mode to \a forward. If \a forward is true,
    only next() and seek() with positive values, are allowed for
    navigating the results.

    Forward only mode can be (depending on the driver) more memory
    efficient since results do not need to be cached. It will also
    improve performance on some databases. For this to be true, you
    must call \c setForwardMode() before the query is prepared or
    executed. Note that the constructor that takes a query and a
    database may execute the query.

    Forward only mode is off by default.

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

/*!
    Returns a QSqlRecord containing the field information for the
    current query. If the query points to a valid row (isValid()
    returns true), the record is populated with the row's values.
    An empty record is returned when there is no active query
    (isActive() returns false).

    To retrieve values from a query, value() should be used since
    its index-based lookup is faster.

    In the following example, a \c{SELECT * FROM} query is executed.
    Since the order of the columns is not defined, QSqlRecord::indexOf()
    is used to obtain the index of a column.

    \code
    QSqlQuery q("select * from employees");
    QSqlRecord rec = q.record();

    qDebug() << "Number of columns: " << rec.count();

    int nameCol = rec.indexOf("name"); // index of the field "name"
    while (q.next())
        qDebug() << q.value(nameCol).toString(); // output all names
    \endcode

    \sa value()
*/
QSqlRecord QSqlQuery::record() const
{
    QSqlRecord rec = d->sqlResult->record();

    if (isValid()) {
        for (int i = 0; i < rec.count(); ++i)
            rec.setValue(i, value(i));
    }
    return rec;
}

/*!
    Clears the result set and releases any resources held by the
    query. You should rarely if ever need to call this function.
*/
void QSqlQuery::clear()
{
    *this = QSqlQuery(driver()->createResult());
}

/*!
    Prepares the SQL query \a query for execution. Returns true if the
    query is prepared successfully; otherwise returns false.

    The query may
    contain placeholders for binding values. Both Oracle style
    colon-name (e.g., \c{:surname}), and ODBC style (\c{?})
    placeholders are supported; but they cannot be mixed in the same
    query. See the \l{QSqlQuery examples}{Detailed Description} for examples.

    Portability note: Some databases choose to delay preparing a query until
    it is executed the first time. In this case, preparing a syntactically wrong
    query succeeds, but every consecutive exec() will fail.

    \sa exec(), bindValue(), addBindValue()
*/
bool QSqlQuery::prepare(const QString& query)
{
    if (d->ref != 1) {
        bool fo = isForwardOnly();
        *this = QSqlQuery(driver()->createResult());
        setForwardOnly(fo);
        d->sqlResult->setNumericalPrecisionPolicy(d->precisionPolicy);
    } else {
        d->sqlResult->setActive(false);
        d->sqlResult->setLastError(QSqlError());
        d->sqlResult->setAt(QSql::BeforeFirstRow);
        d->sqlResult->setNumericalPrecisionPolicy(d->precisionPolicy);
    }
    if (!driver()) {
        qWarning("QSqlQuery::prepare: no driver");
        return false;
    }
    if (!driver()->isOpen() || driver()->isOpenError()) {
        qWarning("QSqlQuery::prepare: database not open");
        return false;
    }
    if (query.isEmpty()) {
        qWarning("QSqlQuery::prepare: empty query");
        return false;
    }
#ifdef QT_DEBUG_SQL
    qDebug("\n QSqlQuery::prepare: %s", query.toLocal8Bit().constData());
#endif
    return d->sqlResult->savePrepare(query);
}

/*!
    \overload

    Executes a previously prepared SQL query. Returns true if the
    query executed successfully; otherwise returns false.

    \sa prepare() bindValue() addBindValue() boundValue() boundValues()
*/
bool QSqlQuery::exec()
{
    d->sqlResult->resetBindCount();
    return d->sqlResult->exec();
}

/*! \enum QSqlQuery::BatchExecutionMode

    \value ValuesAsRows - Updates multiple rows. Treats every entry in a QVariantList as a value for updating the next row.
    \value ValuesAsColumns - Updates a single row. Treats every entry in a QVariantList as a single value of an array type.
*/

/*!
    \since 4.2

    Executes a previously prepared SQL query in a batch. All the bound parameters
    have to be lists of variants. If the database doesn't support batch executions,
    the driver will simulate it using conventional exec() calls.

    Returns true if the query is executed successfully; otherwise returns false.

    Example:

    \code
        QSqlQuery q;
        q.prepare("insert into myTable values (?, ?)");

        QVariantList ints;
        ints << 1 << 2 << 3 << 4;
        q.addBindValue(ints);

        QVariantList names;
        names << "Harald" << "Boris" << "Trond" << QVariant(QVariant::String);
        q.addBindValue(names);

        if (!q.execBatch())
            qDebug() << q.lastError();
    \endcode

    The example above inserts four new rows into \c myTable:

    \code
        1  Harald
        2  Boris
        3  Trond
        4  NULL
    \endcode

    To bind NULL values, a null QVariant of the relevant type has to be added to
    the bound QVariantList; for example, \c {QVariant(QVariant::String)} should be
    used if you are using strings.

    Note that every bound QVariantList must contain the same amount of variants.
    Note that the type of the QVariants in a list must not change. For example,
    you cannot mix integer and string variants within a QVariantList.

    The \a mode parameter indicates how the bound QVariantList will be interpreted.
    If \a mode is \c ValuesAsRows, every variant within the QVariantList will be
    interpreted as a value for a new row. \c ValuesAsColumns is a special case
    for the Oracle driver. In this mode, every entry within a QVariantList will
    be interpreted as array-value for an IN or OUT value within a stored procedure.
    Note that this will only work if the IN or OUT value is a table-type consisting
    of only one column of a basic type, for example
    \c{TYPE myType IS TABLE OF VARCHAR(64) INDEX BY BINARY_INTEGER;}

    \sa prepare(), bindValue(), addBindValue()
*/
bool QSqlQuery::execBatch(BatchExecutionMode mode)
{
    return d->sqlResult->execBatch(mode == ValuesAsColumns);
}

/*!
    Set the placeholder \a placeholder to be bound to value \a val in
    the prepared statement. Note that the placeholder mark (e.g \c{:})
    must be included when specifying the placeholder name. If \a paramType
    is QSql::Out or QSql::InOut, the placeholder will be
    overwritten with data from the database after the exec() call.

    To bind a NULL value, use a null QVariant; for example, use
    \c {QVariant(QVariant::String)} if you are binding a string.

    \sa addBindValue(), prepare(), exec(), boundValue() boundValues()
*/
void QSqlQuery::bindValue(const QString& placeholder, const QVariant& val,
                          QSql::ParamType paramType
)
{
    d->sqlResult->bindValue(placeholder, val, paramType);
}

/*!
    \overload

    Set the placeholder in position \a pos to be bound to value \a val
    in the prepared statement. Field numbering starts at 0. If \a paramType
    is QSql::Out or QSql::InOut, the placeholder will be
    overwritten with data from the database after the exec() call.
*/
void QSqlQuery::bindValue(int pos, const QVariant& val, QSql::ParamType paramType)
{
    d->sqlResult->bindValue(pos, val, paramType);
}

/*!
    Adds the value \a val to the list of values when using positional
    value binding. The order of the addBindValue() calls determines
    which placeholder a value will be bound to in the prepared query.
    If \a paramType is QSql::Out or QSql::InOut, the placeholder will
    be overwritten with data from the database after the exec() call.

    To bind a NULL value, use a null QVariant; for example, use
    \c {QVariant(QVariant::String)} if you are binding a string.

    \sa bindValue(), prepare(), exec(), boundValue() boundValues()
*/
void QSqlQuery::addBindValue(const QVariant& val, QSql::ParamType paramType)
{
    d->sqlResult->addBindValue(val, paramType);
}

/*!
    Returns the value for the \a placeholder.

    \sa boundValues() bindValue() addBindValue()
*/
QVariant QSqlQuery::boundValue(const QString& placeholder) const
{
    return d->sqlResult->boundValue(placeholder);
}

/*!
    \overload

    Returns the value for the placeholder at position \a pos.
*/
QVariant QSqlQuery::boundValue(int pos) const
{
    return d->sqlResult->boundValue(pos);
}

/*!
    Returns a map of the bound values.

    With named binding, the bound values can be examined in the
    following ways:

    \quotefromfile snippets/sqldatabase/sqldatabase.cpp
    \skipto examine with named binding
    \skipto QMapIterator
    \printuntil }

    With positional binding, the code becomes:

    \skipto examine with positional binding
    \skipto QList
    \printuntil endl;

    \sa boundValue() bindValue() addBindValue()
*/
QMap<QString,QVariant> QSqlQuery::boundValues() const
{
    QMap<QString,QVariant> map;

    const QVector<QVariant> values(d->sqlResult->boundValues());
    for (int i = 0; i < values.count(); ++i)
        map[d->sqlResult->boundValueName(i)] = values.at(i);
    return map;
}

/*!
    Returns the last query that was successfully executed.

    In most cases this function returns the same string as
    lastQuery(). If a prepared query with placeholders is executed on
    a DBMS that does not support it, the preparation of this query is
    emulated. The placeholders in the original query are replaced with
    their bound values to form a new query. This function returns the
    modified query. It is mostly useful for debugging purposes.

    \sa lastQuery()
*/
QString QSqlQuery::executedQuery() const
{
    return d->sqlResult->executedQuery();
}

/*!
    \fn bool QSqlQuery::prev()

    Use previous() instead.
*/

/*!
    Returns the object ID of the most recent inserted row if the
    database supports it.
    An invalid QVariant will be returned if the query did not
    insert any value or if the database does not report the id back.
    If more than one row was touched by the insert, the behavior is
    undefined.

    Note that for Oracle databases the row's ROWID will be returned,
    while for MySQL databases the row's auto-increment field will
    be returned.

    \sa QSqlDriver::hasFeature()
*/
QVariant QSqlQuery::lastInsertId() const
{
    return d->sqlResult->lastInsertId();
}

/*!
    Instruct the database driver to return numerical values with a precision specified by
    \a precisionPolicy.

    The Oracle driver, for example, retrieves numerical values as strings by default to
    prevent the loss of precision. If the high precision doesn't matter, use this method
    to increase execution speed by bypassing string conversions.

    Note: Drivers that don't support fetching numerical values with low precision will
    ignore the precision policy. You can use QSqlDriver::hasFeature() to find out whether a
    driver supports this feature.

    Note: Setting the precision policy doesn't affect the currently active query. Call
    \l{exec()}{exec(QString)} or prepare() in order to activate the policy.

    \sa QSql::NumericalPrecisionPolicy, numericalPrecisionPolicy()
*/
void QSqlQuery::setNumericalPrecisionPolicy(QSql::NumericalPrecisionPolicy precisionPolicy)
{
    d->precisionPolicy = precisionPolicy;
}

/*!
    Returns the current precision policy.

    \sa QSql::NumericalPrecisionPolicy, setNumericalPrecisionPolicy()
*/
QSql::NumericalPrecisionPolicy QSqlQuery::numericalPrecisionPolicy() const
{
    return d->precisionPolicy;
}

/*!
    \since 4.3.2
    \preliminary

    Instruct the database driver that no more data will be fetched from this
    query until it is re-executed. There is normally no need to call this
    function, but it may be helpful in order to free resources such as locks
    or cursors if you intend to re-use the query at a later time.
    
    Sets the query to inactive. Bound values retain their values.

    This function is new in Qt 4.3.2 and requires that QT_44_API_QSQLQUERY_FINISH
    is defined when compiling your application. It is expected to become part
    of the public API in Qt 4.4.

    \sa prepare() exec() isActive()
*/
void QSqlQuery::finish()
{
    if (isActive()) {
        d->sqlResult->setLastError(QSqlError());
        d->sqlResult->setAt(QSql::BeforeFirstRow);
        d->sqlResult->detachFromResultSet();
        d->sqlResult->setActive(false);
    }
}