线程尝试读取或写入虚拟地址python QtSql

Question

我有两个问题 - 第一次关闭（更重要的是）第二次从QGIS Python运行代码时它失败了“线程试图读取或写入虚拟地址但没有相应的访问”。

第二个问题是，如果我关闭并删除数据库，使用projectView.show（）显示的表是空的，如果我将这些行注释掉，数据会正确显示。

from PyQt4.QtSql import *
from PyQt4.QtGui import *
from qgis.gui import *

db = QSqlDatabase.addDatabase('QODBC')
if db.isValid():
   db.setDatabaseName('DRIVER={SQL Server};SERVER=%s;DATABASE=%s;UID=%s;PWD=%s;'
                    % ('ServerName',
                      'Database',
                       'username',
                       'password'))   

    #print "db.isValid"

    if db.open():
        #print "success"
        query = db.exec_("""SELECT TOP 100 postal_address as address, EASTING as x, NORTHING as y FROM dbo.POSTAL_ADDRESS WHERE postal_address LIKE('%EX3 %')""")

        projectModel = QSqlQueryModel()
        projectModel.setQuery(query)
        projectView = QTableView()
        projectView.setModel(projectModel)

        projectView.show()    

        QMessageBox.warning(None, "Info", "hello")

        query = db.exec_("""SELECT TOP 100 postal_address as address, EASTING as x, NORTHING as y FROM dbo.POSTAL_ADDRESS WHERE postal_address LIKE('%EX2 %')""")

        projectModel = QSqlQueryModel()
        projectModel.setQuery(query)
        projectView = QTableView()
        projectView.setModel(projectModel)

        projectView.show()    

        #db.close()
        #db.removeDatabase('QODBC')       

    else:
        QMessageBox.warning(None, "Info", "Error")
 else:
    QMessageBox.warning(None, "Info", "Error")