目录

增删改查完整代码如下：.cpp文件.h文件

图示结果： 制作一个简单的数据库，可以实现数据的增、删、改、查的图书馆管理，如果在使用数据库后，没有清除记录，那么下一次打开的时候，仍然会保存上一次执行的记录操作。这就是数据库的优势所在，以下是具体的操作以及代码。

一、总结 在Qt中使用书库，执行流程为一下操作： (1)、安装驱动【Qt中的驱动一般情况下是QSQLITE】 (2)、给数据库起名字，或者也可以从组件上获取自定义数据库名字 (3)、打开数据库 (4)、创建表

二、执行增、删、改、查 将以上4步完成之后，那就可以实现数据库的增、删、改、查。我在下面代码中有详细的解释以及操作，很容易理解。

三、主要知识点 (1)、QSqlQuery：类提供了一种执行和操作SQL语句的方法 (2)、QSqlDatabase类：用来处理与数据库的连接 (3)、QSqlError类：用来输出数据库中的错误信息

增

//添加数据库成员 //添加数据时，不要将添加命令写错，不然就会报错，不能实现数据库的添加 void Library::on_addButton_clicked() { QSqlQuery query; //获取组件上的内容 QString name = ui->addnameLE->text(); QString price = ui->addpriceLE->text(); QString author = ui->addAutherLE->text(); QString nums = ui->addNumsLE->text(); QString cmd = QString("insert into library values(\"%1\",\"%2\",\"%3\",\"%4\");").arg(name).arg(price).arg(author).arg(nums); if(!query.exec(cmd))//添加数据库 { qDebug() << "Error to Insert Into Database " << myDatabase.lastError(); return; } //数据添加之后，将小部件清空 ui->addNumsLE->clear(); ui->addpriceLE->clear(); ui->addnameLE->clear(); ui->addAutherLE->clear(); }

删

//删除数据库成员 void Library::on_deleteButton_clicked() { QSqlQuery query; //根据名字删除，或者根据作者删除 QString name = ui->deleleNameLE->text(); QString author = ui->deleteAutherLE->text(); QString cmd = QString("delete from library where name =\"%1\" or author = \"%2\";").arg(name).arg(author); if(!query.exec(cmd))//执行删除命令 { qDebug() << "Error to delete Database " << myDatabase.lastError(); return; } //清除小部件内容 ui->deleleNameLE->clear(); ui->deleteAutherLE->clear(); }

改

//修改数据库成员 void Library::on_updateButton_clicked() { QSqlQuery query; //获取修改之前的组件上的内容 QString name = ui->newUPNameLE->text(); QString price = ui->newUPPriceLE->text(); QString author = ui->newUPAutherLE->text(); QString nums = ui->newUPNumberLE->text(); //获取修改后的组件上的内容 QString nameLast = ui->lastNameUPLE->text(); QString priceLast = ui->lastPrice->text(); QString authorLast = ui->lastAuther->text(); QString numsLast = ui->lastNums->text(); //执行修改指令 QString cmd = QString("update library set name = \"%1\" , price = \"%2\" where name = \"%3\" ;").arg(nameLast).arg(priceLast).arg(name); if(!query.exec(cmd)) { qDebug() << "Error Update to Database" << myDatabase.lastError(); return; } //清除小部件中的内容 ui->lastNameUPLE->clear(); ui->lastNums->clear(); ui->lastPrice->clear(); ui->lastAuther->clear(); ui->newUPNameLE->clear(); ui->newUPPriceLE->clear(); ui->newUPAutherLE->clear(); ui->newUPNumberLE->clear(); }

查

//查询数据库成员 void Library::on_serchButton_clicked() { QSqlQuery query; QString cmd = QString("select * from library");//查询数据库 if(!query.exec(cmd))//判断数据库是否为空 { qDebug() << "Error Select to Database" << myDatabase.lastError(); return; } QSqlRecord record = query.record();//获取当前记录 //获取每一个记录下的索引 int num1 = record.indexOf("name"); int num2 = record.indexOf("price"); int num3 = record.indexOf("author"); int num4 = record.indexOf("nums"); int i=0; int j=0; while (query.next()) { QString info = QString("%1 %2 %3 %4").arg(query.value(num1).toString()).arg(query.value(num2).toDouble()).arg(query.value(num3).toString()).arg(query.value(num4).toInt()); //在表格中显示信息 ui->tableWidget->setItem(i,j ,new QTableWidgetItem(query.value(num1).toString())); ui->tableWidget->setItem(i,j+1,new QTableWidgetItem(query.value(num2).toString())); ui->tableWidget->setItem(i,j+2,new QTableWidgetItem(query.value(num3).toString())); ui->tableWidget->setItem(i,j+3,new QTableWidgetItem(query.value(num4).toString())); i++; } }

完整代码如下：

.cpp文件

这是.cpp文件 #include "library.h" #include "ui_library.h" #include <QSqlQuery> #include <QSqlRecord> #include <QSqlError> #include <QDebug> Library::Library(QWidget *parent) : QMainWindow(parent), ui(new Ui::Library) { ui->setupUi(this); //1、安装驱动 myDatabase = QSqlDatabase::addDatabase("QSQLITE"); //2、给数据库取名字 myDatabase.setDatabaseName("library.db"); //3、打开数据库 if(!myDatabase.open()) { qDebug() << "Error to open database" << myDatabase.lastError(); return; } } Library::~Library() { delete ui; } //创建数据库 void Library::on_createButton_clicked() { QSqlQuery query; /* 创建一个表： 表名：library 成员：name 、price 、 author 、 nums 执行命令：create table （if not exists：如果不存在，则创建）表名（成员 类型,……） */ if(!query.exec("create table if not exists library(name text, price double ,author text, nums int);")) { qDebug() << "Create Table is error" << myDatabase.lastError(); return; } } //添加数据库成员 void Library::on_addButton_clicked() { QSqlQuery query; QString name = ui->addnameLE->text(); QString price = ui->addpriceLE->text(); QString author = ui->addAutherLE->text(); QString nums = ui->addNumsLE->text(); QString cmd = QString("insert into library values(\"%1\",\"%2\",\"%3\",\"%4\");").arg(name).arg(price).arg(author).arg(nums); if(!query.exec(cmd)) { qDebug() << "Error to Insert Into Database " << myDatabase.lastError(); return; } ui->addNumsLE->clear(); ui->addpriceLE->clear(); ui->addnameLE->clear(); ui->addAutherLE->clear(); } //删除数据库成员 void Library::on_deleteButton_clicked() { QSqlQuery query; QString name = ui->deleleNameLE->text(); QString author = ui->deleteAutherLE->text(); QString cmd = QString("delete from library where name =\"%1\" or author = \"%2\";").arg(name).arg(author); if(!query.exec(cmd)) { qDebug() << "Error to delete Database " << myDatabase.lastError(); return; } //清除小部件内容 ui->deleleNameLE->clear(); ui->deleteAutherLE->clear(); } //修改数据库成员 void Library::on_updateButton_clicked() { QSqlQuery query; QString name = ui->newUPNameLE->text(); QString price = ui->newUPPriceLE->text(); QString author = ui->newUPAutherLE->text(); QString nums = ui->newUPNumberLE->text(); QString nameLast = ui->lastNameUPLE->text(); QString priceLast = ui->lastPrice->text(); QString authorLast = ui->lastAuther->text(); QString numsLast = ui->lastNums->text(); QString cmd = QString("update library set name = \"%1\" , price = \"%2\" where name = \"%3\" ;").arg(nameLast).arg(priceLast).arg(name); if(!query.exec(cmd)) { qDebug() << "Error Update to Database" << myDatabase.lastError(); return; } //清除小部件中的内容 ui->lastNameUPLE->clear(); ui->lastNums->clear(); ui->lastPrice->clear(); ui->lastAuther->clear(); ui->newUPNameLE->clear(); ui->newUPPriceLE->clear(); ui->newUPAutherLE->clear(); ui->newUPNumberLE->clear(); } //查询数据库成员 void Library::on_serchButton_clicked() { QSqlQuery query; QString cmd = QString("select * from library");//查询数据库 if(!query.exec(cmd))//判断数据库是否为空 { qDebug() << "Error Select to Database" << myDatabase.lastError(); return; } QSqlRecord record = query.record();//获取当前记录 int num1 = record.indexOf("name"); int num2 = record.indexOf("price"); int num3 = record.indexOf("author"); int num4 = record.indexOf("nums"); int i=0; int j=0; while (query.next()) { QString info = QString("%1 %2 %3 %4").arg(query.value(num1).toString()).arg(query.value(num2).toDouble()).arg(query.value(num3).toString()).arg(query.value(num4).toInt()); //在表格中显示信息 ui->tableWidget->setItem(i,j ,new QTableWidgetItem(query.value(num1).toString())); ui->tableWidget->setItem(i,j+1,new QTableWidgetItem(query.value(num2).toString())); ui->tableWidget->setItem(i,j+2,new QTableWidgetItem(query.value(num3).toString())); ui->tableWidget->setItem(i,j+3,new QTableWidgetItem(query.value(num4).toString())); i++; } } //关闭数据库 void Library::on_closeButton_clicked() { myDatabase.close(); } //删除数据库 void Library::on_deleteButton_2_clicked() { QSqlQuery query; QString cmd = QString("drop table library");//删除整个数据库 query.exec(cmd); }

.h文件

这是.h文件 #ifndef LIBRARY_H #define LIBRARY_H #include <QMainWindow> #include <QSqlDatabase> namespace Ui { class Library; } class Library : public QMainWindow { Q_OBJECT public: explicit Library(QWidget *parent = nullptr); ~Library(); private slots: //1、创建表 void on_createButton_clicked(); //2、添加数据 void on_addButton_clicked(); //3、删除数据 void on_deleteButton_clicked(); //4、更新数据 void on_updateButton_clicked(); //5、查询数据 void on_serchButton_clicked(); //6、关闭数据库 void on_closeButton_clicked(); //7、清空数据库 void on_deleteButton_2_clicked(); private: Ui::Library *ui; QSqlDatabase myDatabase; }; #endif // LIBRARY_H