python3+PyQt5 uses database table view
database
view
This article mainly introduces the use of database table view in python3 PyQt5 in detail, which has certain reference value. Interested friends can refer to it
It is mentioned above that the form can be presented at one time Each field from the same record comes out, but for tables where users want to see multiple records, a tabular view is needed. This article implements an example of quickly turning python Qt gui into 15 chapters by rewriting it in python3 pyqt5. Users can see multiple records at a time.
#!/usr/bin/env python3
import os
import sys
from PyQt5.QtCore import (PYQT_VERSION_STR, QDate, QFile, QRegExp, QVariant, QModelIndex,Qt)
from PyQt5.QtWidgets import (QApplication,QComboBox,
QDateTimeEdit, QDialog, QGridLayout, QHBoxLayout, QLabel,
QLineEdit, QDateEdit,QMessageBox, QPushButton,
QStyleOptionViewItem, QTableView,QVBoxLayout)
from PyQt5.QtGui import QPixmap,QCursor,QRegExpValidator
from PyQt5.QtSql import (QSqlDatabase, QSqlQuery, QSqlRelation,
QSqlRelationalDelegate, QSqlRelationalTableModel,QSqlTableModel)
import qrc_resources
MAC = True
try:
from PyQt5.QtGui import qt_mac_set_native_menubar
except ImportError:
MAC = False
ID = 0
NAME = ASSETID = 1
CATEGORYID = DATE = DESCRIPTION = 2
ROOM = ACTIONID = 3
ACQUIRED = 1
def createFakeData():
import random
print("Dropping tables...")
query = QSqlQuery()
query.exec_("DROP TABLE assets")
query.exec_("DROP TABLE logs")
query.exec_("DROP TABLE actions")
query.exec_("DROP TABLE categories")
QApplication.processEvents()
print("Creating tables...")
query.exec_("""CREATE TABLE actions (
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
name VARCHAR(20) NOT NULL,
description VARCHAR(40) NOT NULL)""")
query.exec_("""CREATE TABLE categories (
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
name VARCHAR(20) NOT NULL,
description VARCHAR(40) NOT NULL)""")
query.exec_("""CREATE TABLE assets (
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
name VARCHAR(40) NOT NULL,
categoryid INTEGER NOT NULL,
room VARCHAR(4) NOT NULL,
FOREIGN KEY (categoryid) REFERENCES categories)""")
query.exec_("""CREATE TABLE logs (
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
assetid INTEGER NOT NULL,
date DATE NOT NULL,
actionid INTEGER NOT NULL,
FOREIGN KEY (assetid) REFERENCES assets,
FOREIGN KEY (actionid) REFERENCES actions)""")
QApplication.processEvents()
print("Populating tables...")
query.exec_("INSERT INTO actions (name, description) "
"VALUES ('Acquired', 'When installed')")
query.exec_("INSERT INTO actions (name, description) "
"VALUES ('Broken', 'When failed and unusable')")
query.exec_("INSERT INTO actions (name, description) "
"VALUES ('Repaired', 'When back in service')")
query.exec_("INSERT INTO actions (name, description) "
"VALUES ('Routine maintenance', "
"'When tested, refilled, etc.')")
query.exec_("INSERT INTO categories (name, description) VALUES "
"('Computer Equipment', "
"'Monitors, System Units, Peripherals, etc.')")
query.exec_("INSERT INTO categories (name, description) VALUES "
"('Furniture', 'Chairs, Tables, Desks, etc.')")
query.exec_("INSERT INTO categories (name, description) VALUES "
"('Electrical Equipment', 'Non-computer electricals')")
today = QDate.currentDate()
floors = list(range(1, 12)) + list(range(14, 28))
monitors = (('17" LCD Monitor', 1),
('20" LCD Monitor', 1),
('21" LCD Monitor', 1),
('21" CRT Monitor', 1),
('24" CRT Monitor', 1))
computers = (("Computer (32-bit/80GB/0.5GB)", 1),
("Computer (32-bit/100GB/1GB)", 1),
("Computer (32-bit/120GB/1GB)", 1),
("Computer (64-bit/240GB/2GB)", 1),
("Computer (64-bit/320GB/4GB)", 1))
printers = (("Laser Printer (4 ppm)", 1),
("Laser Printer (6 ppm)", 1),
("Laser Printer (8 ppm)", 1),
("Laser Printer (16 ppm)", 1))
chairs = (("Secretary Chair", 2),
("Executive Chair (Basic)", 2),
("Executive Chair (Ergonimic)", 2),
("Executive Chair (Hi-Tech)", 2))
desks = (("Desk (Basic, 3 drawer)", 2),
("Desk (Standard, 3 drawer)", 2),
("Desk (Executive, 3 drawer)", 2),
("Desk (Executive, 4 drawer)", 2),
("Desk (Large, 4 drawer)", 2))
furniture = (("Filing Cabinet (3 drawer)", 2),
("Filing Cabinet (4 drawer)", 2),
("Filing Cabinet (5 drawer)", 2),
("Bookcase (4 shelves)", 2),
("Bookcase (6 shelves)", 2),
("Table (4 seater)", 2),
("Table (8 seater)", 2),
("Table (12 seater)", 2))
electrical = (("Fan (3 speed)", 3),
("Fan (5 speed)", 3),
("Photocopier (4 ppm)", 3),
("Photocopier (6 ppm)", 3),
("Photocopier (8 ppm)", 3),
("Shredder", 3))
query.prepare("INSERT INTO assets (name, categoryid, room) "
"VALUES (:name, :categoryid, :room)")
logQuery = QSqlQuery()
logQuery.prepare("INSERT INTO logs (assetid, date, actionid) "
"VALUES (:assetid, :date, :actionid)")
assetid = 1
for i in range(20):
room = "{0:02d}{1:02d}".format(
random.choice(floors), random.randint(1, 62))
for name, category in (random.choice(monitors),
random.choice(computers), random.choice(chairs),
random.choice(desks), random.choice(furniture)):
query.bindValue(":name", name)
query.bindValue(":categoryid", category)
query.bindValue(":room", room)
query.exec_()
logQuery.bindValue(":assetid", assetid)
when = today.addDays(-random.randint(7, 1500))
#when=when.toString()
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid", ACQUIRED)
logQuery.exec_()
if random.random() > 0.7:
logQuery.bindValue(":assetid", assetid)
when = when.addDays(random.randint(1, 1500))
if when <= today:
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid",
random.choice((2, 4)))
logQuery.exec_()
assetid += 1
if random.random() > 0.8:
name, category = random.choice(printers)
query.bindValue(":name", name)
query.bindValue(":categoryid", category)
query.bindValue(":room", room)
query.exec_()
logQuery.bindValue(":assetid", assetid)
when = today.addDays(-random.randint(7, 1500))
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid",ACQUIRED)
logQuery.exec_()
if random.random() > 0.6:
logQuery.bindValue(":assetid", assetid)
when = when.addDays(random.randint(1, 1500))
if when <= today:
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid",
random.choice((2, 4)))
logQuery.exec_()
assetid += 1
if random.random() > 0.6:
name, category = random.choice(electrical)
query.bindValue(":name", name)
query.bindValue(":categoryid", category)
query.bindValue(":room", room)
query.exec_()
logQuery.bindValue(":assetid", assetid)
when = today.addDays(-random.randint(7, 1500))
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid",ACQUIRED)
logQuery.exec_()
if random.random() > 0.5:
logQuery.bindValue(":assetid", assetid)
when = when.addDays(random.randint(1, 1500))
if when <= today:
logQuery.bindValue(":date", when.toString("yyyy-MM-dd"))
logQuery.bindValue(":actionid",
random.choice((2, 4)))
logQuery.exec_()
assetid += 1
QApplication.processEvents()
print("Assets:")
query.exec_("SELECT id, name, categoryid, room FROM assets "
"ORDER by id")
categoryQuery = QSqlQuery()
while query.next():
id = query.value(0)
name = str(query.value(1))
categoryid = query.value(2)
room = str(query.value(3))
categoryQuery.exec_("SELECT name FROM categories "
"WHERE id = {0}".format(categoryid))
category = "{0}".format(categoryid)
if categoryQuery.next():
category = str(categoryQuery.value(0))
print("{0}: {1} [{2}] {3}".format(id, name, category, room))
QApplication.processEvents()
class ReferenceDataDlg(QDialog):
def __init__(self, table, title, parent=None):
super(ReferenceDataDlg, self).__init__(parent)
self.model = QSqlTableModel(self)
self.model.setTable(table)
self.model.setSort(NAME, Qt.AscendingOrder)
self.model.setHeaderData(ID, Qt.Horizontal,"ID")
self.model.setHeaderData(NAME, Qt.Horizontal, "Name")
self.model.setHeaderData(DESCRIPTION, Qt.Horizontal,"Description")
self.model.select()
self.view = QTableView()
self.view.setModel(self.model)
self.view.setSelectionMode(QTableView.SingleSelection)
self.view.setSelectionBehavior(QTableView.SelectRows)
self.view.setColumnHidden(ID, True)
self.view.resizeColumnsToContents()
addButton = QPushButton("&Add")
deleteButton = QPushButton("&Delete")
okButton = QPushButton("&OK")
if not MAC:
addButton.setFocusPolicy(Qt.NoFocus)
deleteButton.setFocusPolicy(Qt.NoFocus)
buttonLayout = QHBoxLayout()
buttonLayout.addWidget(addButton)
buttonLayout.addWidget(deleteButton)
buttonLayout.addStretch()
buttonLayout.addWidget(okButton)
layout = QVBoxLayout()
layout.addWidget(self.view)
layout.addLayout(buttonLayout)
self.setLayout(layout)
addButton.clicked.connect(self.addRecord)
deleteButton.clicked.connect(self.deleteRecord)
okButton.clicked.connect(self.accept)
self.setWindowTitle(
"Asset Manager - Edit {0} Reference Data".format(title))
def addRecord(self):
row = self.model.rowCount()
self.model.insertRow(row)
index = self.model.index(row, NAME)
self.view.setCurrentIndex(index)
self.view.edit(index)
def deleteRecord(self):
index = self.view.currentIndex()
if not index.isValid():
return
#QSqlDatabase.database().transaction()
record = self.model.record(index.row())
id = record.value(ID)
table = self.model.tableName()
query = QSqlQuery()
if table == "actions":
query.exec_("SELECT COUNT(*) FROM logs "
"WHERE actionid = {0}".format(id))
elif table == "categories":
query.exec_("SELECT COUNT(*) FROM assets "
"WHERE categoryid = {0}".format(id))
count = 0
if query.next():
count = query.value(0)
if count:
QMessageBox.information(self,
"Delete {0}".format(table),
("Cannot delete {0}<br>"
"from the {1} table because it is used by "
"{2} records").format(record.value(NAME),table,count))
#QSqlDatabase.database().rollback()
return
self.model.removeRow(index.row())
self.model.submitAll()
self.model.select()
#QSqlDatabase.database().commit()
class AssetDelegate(QSqlRelationalDelegate):
def __init__(self, parent=None):
super(AssetDelegate, self).__init__(parent)
def paint(self, painter, option, index):
myoption = QStyleOptionViewItem(option)
if index.column() == ROOM:
myoption.displayAlignment |= (Qt.AlignRight|Qt.AlignVCenter)
QSqlRelationalDelegate.paint(self, painter, myoption, index)
def createEditor(self, parent, option, index):
if index.column() == ROOM:
editor = QLineEdit(parent)
regex = QRegExp(r"(?:0[1-9]|1[0124-9]|2[0-7])"
r"(?:0[1-9]|[1-5][0-9]|6[012])")
validator = QRegExpValidator(regex, parent)
editor.setValidator(validator)
editor.setInputMask("9999")
editor.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
return editor
else:
return QSqlRelationalDelegate.createEditor(self, parent,
option, index)
def setEditorData(self, editor, index):
if index.column() == ROOM:
text = index.model().data(index, Qt.DisplayRole)
editor.setText(text)
else:
QSqlRelationalDelegate.setEditorData(self, editor, index)
def setModelData(self, editor, model, index):
if index.column() == ROOM:
model.setData(index, editor.text())
else:
QSqlRelationalDelegate.setModelData(self, editor, model,
index)
class LogDelegate(QSqlRelationalDelegate):
def __init__(self, parent=None):
super(LogDelegate, self).__init__(parent)
def paint(self, painter, option, index):
myoption = QStyleOptionViewItem(option)
if index.column() == DATE:
myoption.displayAlignment |= (Qt.AlignRight|Qt.AlignVCenter)
QSqlRelationalDelegate.paint(self, painter, myoption, index)
def createEditor(self, parent, option, index):
if (index.column() == ACTIONID and
index.model().data(index, Qt.DisplayRole) ==
ACQUIRED): # Acquired is read-only
return
if index.column() == DATE:
editor = QDateEdit(parent)
editor.setMaximumDate(QDate.currentDate())
editor.setDisplayFormat("yyyy-MM-dd")
if PYQT_VERSION_STR >= "4.1.0":
editor.setCalendarPopup(True)
editor.setAlignment(Qt.AlignRight|
Qt.AlignVCenter)
return editor
else:
return QSqlRelationalDelegate.createEditor(self, parent,
option, index)
def setEditorData(self, editor, index):
if index.column() == DATE:
date = index.model().data(index, Qt.DisplayRole)
editor.setDate(date)
else:
QSqlRelationalDelegate.setEditorData(self, editor, index)
def setModelData(self, editor, model, index):
if index.column() == DATE:
model.setData(index, QVariant(editor.date()))
else:
QSqlRelationalDelegate.setModelData(self, editor, model,
index)
class MainForm(QDialog):
def __init__(self):
super(MainForm, self).__init__()
self.assetModel = QSqlRelationalTableModel(self)
self.assetModel.setTable("assets")
self.assetModel.setRelation(CATEGORYID,
QSqlRelation("categories", "id", "name"))
self.assetModel.setSort(ROOM, Qt.AscendingOrder)
self.assetModel.setHeaderData(ID, Qt.Horizontal,"ID")
self.assetModel.setHeaderData(NAME, Qt.Horizontal,"Name")
self.assetModel.setHeaderData(CATEGORYID, Qt.Horizontal,"Category")
self.assetModel.setHeaderData(ROOM, Qt.Horizontal,"Room")
self.assetModel.select()
self.assetView = QTableView()
self.assetView.setModel(self.assetModel)
self.assetView.setItemDelegate(AssetDelegate(self))
self.assetView.setSelectionMode(QTableView.SingleSelection)
self.assetView.setSelectionBehavior(QTableView.SelectRows)
self.assetView.setColumnHidden(ID, True)
self.assetView.resizeColumnsToContents()
assetLabel = QLabel("A&ssets")
assetLabel.setBuddy(self.assetView)
self.logModel = QSqlRelationalTableModel(self)
self.logModel.setTable("logs")
self.logModel.setRelation(ACTIONID,
QSqlRelation("actions", "id", "name"))
self.logModel.setSort(DATE, Qt.AscendingOrder)
self.logModel.setHeaderData(DATE, Qt.Horizontal, "Date")
self.logModel.setHeaderData(ACTIONID, Qt.Horizontal,"Action")
self.logModel.select()
self.logView = QTableView()
self.logView.setModel(self.logModel)
self.logView.setItemDelegate(LogDelegate(self))
self.logView.setSelectionMode(QTableView.SingleSelection)
self.logView.setSelectionBehavior(QTableView.SelectRows)
self.logView.setColumnHidden(ID, True)
self.logView.setColumnHidden(ASSETID, True)
self.logView.resizeColumnsToContents()
self.logView.horizontalHeader().setStretchLastSection(True)
logLabel = QLabel("&Logs")
logLabel.setBuddy(self.logView)
addAssetButton = QPushButton("&Add Asset")
deleteAssetButton = QPushButton("&Delete Asset")
addActionButton = QPushButton("Add A&ction")
deleteActionButton = QPushButton("Delete Ac&tion")
editActionsButton = QPushButton("&Edit Actions...")
editCategoriesButton = QPushButton("Ed&it Categories...")
quitButton = QPushButton("&Quit")
for button in (addAssetButton, deleteAssetButton,
addActionButton, deleteActionButton,
editActionsButton, editCategoriesButton, quitButton):
if MAC:
button.setDefault(False)
button.setAutoDefault(False)
else:
button.setFocusPolicy(Qt.NoFocus)
dataLayout = QVBoxLayout()
dataLayout.addWidget(assetLabel)
dataLayout.addWidget(self.assetView, 1)
dataLayout.addWidget(logLabel)
dataLayout.addWidget(self.logView)
buttonLayout = QVBoxLayout()
buttonLayout.addWidget(addAssetButton)
buttonLayout.addWidget(deleteAssetButton)
buttonLayout.addWidget(addActionButton)
buttonLayout.addWidget(deleteActionButton)
buttonLayout.addWidget(editActionsButton)
buttonLayout.addWidget(editCategoriesButton)
buttonLayout.addStretch()
buttonLayout.addWidget(quitButton)
layout = QHBoxLayout()
layout.addLayout(dataLayout, 1)
layout.addLayout(buttonLayout)
self.setLayout(layout)
#self.connect(self.assetView.selectionModel(),
#SIGNAL(("currentRowChanged(QModelIndex,QModelIndex)")),
#self.assetChanged)
self.assetView.selectionModel().currentRowChanged.connect(self.assetChanged)
addAssetButton.clicked.connect(self.addAsset)
deleteAssetButton.clicked.connect(self.deleteAsset)
addActionButton.clicked.connect(self.addAction)
deleteActionButton.clicked.connect(self.deleteAction)
editActionsButton.clicked.connect(self.editActions)
editCategoriesButton.clicked.connect(self.editCategories)
quitButton.clicked.connect(self.done)
self.assetChanged(self.assetView.currentIndex())
self.setMinimumWidth(650)
self.setWindowTitle("Asset Manager")
def done(self, result=1):
query = QSqlQuery()
query.exec_("DELETE FROM logs WHERE logs.assetid NOT IN"
"(SELECT id FROM assets)")
QDialog.done(self, 1)
def assetChanged(self, index):
if index.isValid():
record = self.assetModel.record(index.row())
#print(index.row())
id = record.value("id")
self.logModel.setFilter("assetid = {0}".format(id))
else:
self.logModel.setFilter("assetid = -1")
#self.logModel.reset() # workaround for Qt <= 4.3.3/SQLite bug
#self.logModel.beginResetModel()
self.logModel.select()
self.logView.horizontalHeader().setVisible(
self.logModel.rowCount() > 0)
if PYQT_VERSION_STR < "4.1.0":
self.logView.setColumnHidden(ID, True)
self.logView.setColumnHidden(ASSETID, True)
#self.logModel.endResetModel()
def addAsset(self):
row = (self.assetView.currentIndex().row()
if self.assetView.currentIndex().isValid() else 0)
QSqlDatabase.database().transaction()
self.assetModel.insertRow(row)
index = self.assetModel.index(row, NAME)
self.assetView.setCurrentIndex(index)
assetid = 1
query = QSqlQuery()
query.exec_("SELECT MAX(id) FROM assets")
if query.next():
assetid = query.value(0)
query.prepare("INSERT INTO logs (assetid, date, actionid) "
"VALUES (:assetid, :date, :actionid)")
query.bindValue(":assetid", assetid + 1)
query.bindValue(":date", QDate.currentDate())
query.bindValue(":actionid", ACQUIRED)
query.exec_()
QSqlDatabase.database().commit()
#self.logModel.select()
self.assetView.edit(index)
def deleteAsset(self):
index = self.assetView.currentIndex()
if not index.isValid():
return
QSqlDatabase.database().transaction()
record = self.assetModel.record(index.row())
assetid = record.value(ID)
logrecords = 1
query = QSqlQuery("SELECT COUNT(*) FROM logs WHERE assetid = {0}".format(assetid))
if query.next():
logrecords = query.value(0)
msg = ("<font color=red>Delete</font><br><b>{0}</b>"
"<br>from room {1}").format(record.value(NAME),record.value(ROOM))
if logrecords > 1:
msg += (", along with {0} log records"
.format(logrecords))
msg += "?"
if (QMessageBox.question(self, "Delete Asset", msg,
QMessageBox.Yes|QMessageBox.No) ==
QMessageBox.No):
QSqlDatabase.database().rollback()
return
#query.exec_("DELETE FROM logs WHERE assetid = {0}"
# .format(assetid))
#use model API
self.logModel.setFilter("assetid={0}".format(assetid))
self.logModel.select()
if self.logModel.rowCount()>0:
self.logModel.removeRows(0,self.logModel.rowCount())
self.logModel.submitAll()
self.assetModel.removeRow(index.row())
self.assetModel.submitAll()
QSqlDatabase.database().commit()
self.assetModel.select()
self.assetChanged(self.assetView.currentIndex())
def addAction(self):
index = self.assetView.currentIndex()
if not index.isValid():
return
QSqlDatabase.database().transaction()
record = self.assetModel.record(index.row())
assetid = record.value(ID)
row = self.logModel.rowCount()
self.logModel.insertRow(row)
self.logModel.setData(self.logModel.index(row, ASSETID),
assetid)
self.logModel.setData(self.logModel.index(row, DATE),
QDate.currentDate())
QSqlDatabase.database().commit()
index = self.logModel.index(row, ACTIONID)
self.logView.setCurrentIndex(index)
self.logView.edit(index)
def deleteAction(self):
index = self.logView.currentIndex()
if not index.isValid():
return
record = self.logModel.record(index.row())
action = record.value(ACTIONID)
if action == "Acquired":
QMessageBox.information(self, "Delete Log",
"The 'Acquired' log record cannot be deleted.<br>"
"You could delete the entire asset instead.")
return
when = str(record.value(DATE))
if (QMessageBox.question(self, "Delete Log",
"Delete log<br>{0} {1}?".format(when, action),
QMessageBox.Yes|QMessageBox.No) ==
QMessageBox.No):
return
self.logModel.removeRow(index.row())
self.logModel.submitAll()
self.logModel.select()
def editActions(self):
form = ReferenceDataDlg("actions", "Action", self)
form.exec_()
def editCategories(self):
form = ReferenceDataDlg("categories", "Category", self)
form.exec_()
def main():
app = QApplication(sys.argv)
filename = os.path.join(os.path.dirname(__file__), "assets.db")
create = not QFile.exists(filename)
db = QSqlDatabase.addDatabase("QSQLITE")
db.setDatabaseName(filename)
if not db.open():
QMessageBox.warning(None, "Asset Manager",
("Database Error: {0}"
.format(db.lastError().text())))
sys.exit(1)
splash = None
if create:
app.setOverrideCursor(QCursor(Qt.WaitCursor))
splash = QLabel()
pixmap = QPixmap(":/assetmanagersplash.png")
splash.setPixmap(pixmap)
splash.setMask(pixmap.createHeuristicMask())
splash.setWindowFlags(Qt.SplashScreen)
rect = app.desktop().availableGeometry()
splash.move((rect.width() - pixmap.width()) / 2,
(rect.height() - pixmap.height()) / 2)
splash.show()
app.processEvents()
createFakeData()
form = MainForm()
form.show()
if create:
splash.close()
app.processEvents()
app.restoreOverrideCursor()
app.exec_()
del form
del db
main()Copy after login
Running results:
python3 PyQt5 implements drag and drop function
python3 Detailed explanation of PyQt5 custom view
python3 Detailed explanation of PyQt5 generic delegate
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How does Hibernate implement polymorphic mapping?
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Hibernate polymorphic mapping can map inherited classes to the database and provides the following mapping types: joined-subclass: Create a separate table for the subclass, including all columns of the parent class. table-per-class: Create a separate table for subclasses, containing only subclass-specific columns. union-subclass: similar to joined-subclass, but the parent class table unions all subclass columns.
iOS 18 adds a new 'Recovered' album function to retrieve lost or damaged photos
Jul 18, 2024 am 05:48 AM
Apple's latest releases of iOS18, iPadOS18 and macOS Sequoia systems have added an important feature to the Photos application, designed to help users easily recover photos and videos lost or damaged due to various reasons. The new feature introduces an album called "Recovered" in the Tools section of the Photos app that will automatically appear when a user has pictures or videos on their device that are not part of their photo library. The emergence of the "Recovered" album provides a solution for photos and videos lost due to database corruption, the camera application not saving to the photo library correctly, or a third-party application managing the photo library. Users only need a few simple steps
An in-depth analysis of how HTML reads the database
Apr 09, 2024 pm 12:36 PM
HTML cannot read the database directly, but it can be achieved through JavaScript and AJAX. The steps include establishing a database connection, sending a query, processing the response, and updating the page. This article provides a practical example of using JavaScript, AJAX and PHP to read data from a MySQL database, showing how to dynamically display query results in an HTML page. This example uses XMLHttpRequest to establish a database connection, send a query and process the response, thereby filling data into page elements and realizing the function of HTML reading the database.
How to handle database connection errors in PHP
Jun 05, 2024 pm 02:16 PM
To handle database connection errors in PHP, you can use the following steps: Use mysqli_connect_errno() to obtain the error code. Use mysqli_connect_error() to get the error message. By capturing and logging these error messages, database connection issues can be easily identified and resolved, ensuring the smooth running of your application.
Detailed tutorial on establishing a database connection using MySQLi in PHP
Jun 04, 2024 pm 01:42 PM
How to use MySQLi to establish a database connection in PHP: Include MySQLi extension (require_once) Create connection function (functionconnect_to_db) Call connection function ($conn=connect_to_db()) Execute query ($result=$conn->query()) Close connection ( $conn->close())
Tips and practices for handling Chinese garbled characters in databases with PHP
Mar 27, 2024 pm 05:21 PM
PHP is a back-end programming language widely used in website development. It has powerful database operation functions and is often used to interact with databases such as MySQL. However, due to the complexity of Chinese character encoding, problems often arise when dealing with Chinese garbled characters in the database. This article will introduce the skills and practices of PHP in handling Chinese garbled characters in databases, including common causes of garbled characters, solutions and specific code examples. Common reasons for garbled characters are incorrect database character set settings: the correct character set needs to be selected when creating the database, such as utf8 or u
How to use database callback functions in Golang?
Jun 03, 2024 pm 02:20 PM
Using the database callback function in Golang can achieve: executing custom code after the specified database operation is completed. Add custom behavior through separate functions without writing additional code. Callback functions are available for insert, update, delete, and query operations. You must use the sql.Exec, sql.QueryRow, or sql.Query function to use the callback function.
