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📜  PyQt-数据库处理

📅  最后修改于: 2020-11-08 08:12:39             🧑  作者: Mango

PyQt API包含精心设计的类系统，可与许多基于SQL的数据库进行通信。它的QSqlDatabase提供通过Connection对象的访问。以下是当前可用的SQL驱动程序的列表-

Sr.No. Driver Type & Description
1

QDB2

IBM DB2
2

QIBASE

Borland InterBase Driver
3

QMYSQL

MySQL Driver
4

QOCI

Oracle Call Interface Driver
5

QODBC

ODBC Driver (includes Microsoft SQL Server)
6

QPSQL

PostgreSQL Driver
7

QSQLITE

SQLite version 3 or above
8

QSQLITE2

SQLite version 2

例

使用静态方法建立与SQLite数据库的连接-

db = QtSql.QSqlDatabase.addDatabase('QSQLITE')
db.setDatabaseName('sports.db')

QSqlDatabase类的其他方法如下-

Sr.No. Methods & Description
1

setDatabaseName()

Sets the name of the database with which connection is sought
2

setHostName()

Sets the name of the host on which the database is installed
3

setUserName()

Specifies the user name for connection
4

setPassword()

Sets the connection object’s password if any
5

commit()

Commits the transactions and returns true if successful
6

rollback()

Rolls back the database transaction
7

close()

Closes the connection

QSqlQuery类具有执行和操纵SQL命令的功能。可以执行DDL和DML类型的SQL查询。该类中最重要的方法是exec_()，该方法将包含要执行的SQL语句的字符串作为参数。

query = QtSql.QSqlQuery()
query.exec_("create table sportsmen(id int primary key, 
   " "firstname varchar(20), lastname varchar(20))")

以下脚本创建一个SQLite数据库sports.db，其中包含一个填充了五个记录的Sportsperson表。

from PyQt4 import QtSql, QtGui

def createDB():
   db = QtSql.QSqlDatabase.addDatabase('QSQLITE')
   db.setDatabaseName('sports.db')
    
   if not db.open():
      QtGui.QMessageBox.critical(None, QtGui.qApp.tr("Cannot open database"),
         QtGui.qApp.tr("Unable to establish a database connection.\n"
            "This example needs SQLite support. Please read "
            "the Qt SQL driver documentation for information "
            "how to build it.\n\n" "Click Cancel to exit."),
         QtGui.QMessageBox.Cancel)
            
      return False
        
   query = QtSql.QSqlQuery()
    
   query.exec_("create table sportsmen(id int primary key, "
      "firstname varchar(20), lastname varchar(20))")
        
   query.exec_("insert into sportsmen values(101, 'Roger', 'Federer')")
   query.exec_("insert into sportsmen values(102, 'Christiano', 'Ronaldo')")
   query.exec_("insert into sportsmen values(103, 'Ussain', 'Bolt')")
   query.exec_("insert into sportsmen values(104, 'Sachin', 'Tendulkar')")
   query.exec_("insert into sportsmen values(105, 'Saina', 'Nehwal')")
   return True
    
if __name__ == '__main__':
   import sys
    
   app = QtGui.QApplication(sys.argv)
   createDB()

PyQt中的QSqlTableModel类是一个高级接口，它提供可编辑的数据模型来读取和写入单个表中的记录。该模型用于填充QTableView对象。它为用户提供了一个可滚动和可编辑的视图，可以将其放在任何顶级窗口中。

QTableModel对象以以下方式声明-

model = QtSql.QSqlTableModel()

可以将其编辑策略设置为以下任意一种：

QSqlTableModel.OnFieldChange All changes will be applied immediately
QSqlTableModel.OnRowChange Changes will be applied when the user selects a different row
QSqlTableModel.OnManualSubmit All changes will be cached until either submitAll() or revertAll() is called

例

在以下示例中，运动员表用作模型，策略设置为-

model.setTable('sportsmen') 
model.setEditStrategy(QtSql.QSqlTableModel.OnFieldChange)

   model.select()

QTableView类是PyQt中Model / View框架的一部分。 QTableView对象创建如下-

view = QtGui.QTableView()
view.setModel(model)
view.setWindowTitle(title)
return view

这个QTableView对象和两个QPushButton小部件被添加到顶级QDialog窗口中。添加按钮的clicked()信号连接到addrow()，后者在模型表上执行insertRow()。

button.clicked.connect(addrow)
def addrow():
   print model.rowCount()
   ret = model.insertRows(model.rowCount(), 1)
   print ret

与删除按钮关联的Slot执行lambda函数，该函数删除用户选择的行。

btn1.clicked.connect(lambda: model.removeRow(view1.currentIndex().row()))

完整的代码如下-

import sys
from PyQt4 import QtCore, QtGui, QtSql
import sportsconnection

def initializeModel(model):
   model.setTable('sportsmen')
   model.setEditStrategy(QtSql.QSqlTableModel.OnFieldChange)
   model.select()
   model.setHeaderData(0, QtCore.Qt.Horizontal, "ID")
   model.setHeaderData(1, QtCore.Qt.Horizontal, "First name")
   model.setHeaderData(2, QtCore.Qt.Horizontal, "Last name")
    
def createView(title, model):
   view = QtGui.QTableView()
   view.setModel(model)
   view.setWindowTitle(title)
   return view
    
def addrow():
   print model.rowCount()
   ret = model.insertRows(model.rowCount(), 1)
   print ret
    
def findrow(i):
   delrow = i.row()
    
if __name__ == '__main__':

   app = QtGui.QApplication(sys.argv)
   db = QtSql.QSqlDatabase.addDatabase('QSQLITE')
   db.setDatabaseName('sports.db')
   model = QtSql.QSqlTableModel()
   delrow = -1
   initializeModel(model)
    
   view1 = createView("Table Model (View 1)", model)
   view1.clicked.connect(findrow)
    
   dlg = QtGui.QDialog()
   layout = QtGui.QVBoxLayout()
   layout.addWidget(view1)
    
   button = QtGui.QPushButton("Add a row")
   button.clicked.connect(addrow)
   layout.addWidget(button)
    
   btn1 = QtGui.QPushButton("del a row")
   btn1.clicked.connect(lambda: model.removeRow(view1.currentIndex().row()))
   layout.addWidget(btn1)
    
   dlg.setLayout(layout)
   dlg.setWindowTitle("Database Demo")
   dlg.show()
   sys.exit(app.exec_())

上面的代码产生以下输出-

数据库处理输出