C/C++编程：Qt数据库QSql增删改查组件的实战应用

Qt SQL模块是Qt中用来操作数据库的类，该类封装了各种SQL数据库接口，可以很方便的链接并使用，数据的获取也使用了典型的Model/View结构，通过MV结构映射我们可以实现数据与通用组件的灵活绑定，一般SQL组件常用的操作，包括，读取数据，插入数据，更新数据，删除数据，这四个功能我将分别介绍它是如何使用的。

SQL模块在使用时必须引入模块，需要在pro文件内增加QT += sql并在头文件内增加#include <QSqlDatabase>导入模块才可以正常使用。

初始化数据库: 初始化调用QSqlDatabase::addDatabase指定数据库类型,通过db.setDatabaseName()指定数据库文件名.

#include <QCoreApplication>#include <QSqlDatabase>#include <QSqlError>#include <QSqlQuery>#include <QSqlRecord>#include <iostream>#include <QStringList>#include <QString>#include <QVariant>// 初始化表结构// https://www.cnblogs.com/lysharkbool InitSQL(){    // 指定数据库驱动类型    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("./lyshark.db");     if (!db.open())     {            std::cout << db.lastError().text().toStdString()<< std::endl;            return false;     }    // 执行SQL创建表    db.exec("DROP TABLE LyShark");    db.exec("CREATE TABLE LyShark ("                    "id INTEGER PRIMARY KEY AUTOINCREMENT, "                    "name VARCHAR(40) NOT NULL, "                    "age INTEGER NOT NULL)"         );    // 提交事务请求    bool ref = db.commit();    db.close();    return ref;}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    bool ref = InitSQL();    std::cout << "init: " << ref << std::endl;    return a.exec();}

初始化表结构如下:

逐条插入数据: 逐条插入记录在Qt中可直接调用SQL模块提供的db.exec()函数,插入后最后需要调用db.commit()一次性提交事务.

#include <QCoreApplication>#include <QSqlDatabase>#include <QSqlError>#include <QSqlQuery>#include <QSqlRecord>#include <iostream>#include <QStringList>#include <QString>#include <QVariant>// 逐条插入数据// https://www.cnblogs.com/lysharkbool InsertSQL(){    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("./lyshark.db");     if (!db.open())     {            std::cout << db.lastError().text().toStdString()<< std::endl;            return false;     }     // 逐条插入数据     db.exec("INSERT INTO LyShark(name,age) ""VALUES ('admin',23)");     db.exec("INSERT INTO LyShark(name,age) ""VALUES ('zhangsan',25)");     db.exec("INSERT INTO LyShark(name,age) ""VALUES ('lisi',34)");     // 提交数据     bool ref = db.commit();     return ref;}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    bool ref = InsertSQL();    std::cout << "insert = > " << ref << std::endl;    return a.exec();}

插入记录如下:

多条记录插入: 一次性插入多条数据记录,可调用query.prepare()绑定字段与SQL记录,绑定后即可通过循环批量插入记录.

#include <QCoreApplication>#include <QSqlDatabase>#include <QSqlError>#include <QSqlQuery>#include <QSqlRecord>#include <iostream>#include <QStringList>#include <QString>#include <QVariant>// 批量插入数据// https://www.cnblogs.com/lysharkbool InsertMultipleSQL(){    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("./lyshark.db");    if (!db.open())    {           std::cout << db.lastError().text().toStdString()<< std::endl;           return false;    }    // 定义字符串链表    QStringList user_name;    QStringList user_age;    // 批量插入数据到链表中    user_name << "www.lyshark.com" << "https://www.cnblogs.com/lyshark" << "lyshark";    user_age << "22" << "33" << "44";    // 绑定数据记录    QSqlQuery query;    query.prepare("INSERT INTO LyShark(name,age) ""VALUES (:name, :age)");    // 判断两张表中字段数据量是否一致    if(user_name.size() == user_age.size())    {        // 循环插入数据        for(int x=0;x< user_name.size(); x++)        {            query.bindValue(":name",user_name[x]);            query.bindValue(":age",user_age[x]);            query.exec();        }    }    // 提交数据    db.commit();}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    bool ref = InsertMultipleSQL();    std::cout << "insert = > " << ref << std::endl;    return a.exec();}

批量插入数据如下:

查询表中记录: 查询记录可调用QSqlQuery query()得到记录条数,然后不断循环,每次循环调用一次query.next()获取一条,直到循环结束.

#include <QCoreApplication>#include <QSqlDatabase>#include <QSqlError>#include <QSqlQuery>#include <QSqlRecord>#include <iostream>#include <QStringList>#include <QString>#include <QVariant>// 查询数据记录// https://www.cnblogs.com/lysharkbool SelectSQL(){    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("./lyshark.db");     if (!db.open())     {            std::cout << db.lastError().text().toStdString()<< std::endl;            return false;     }     // 查询数据     QSqlQuery query("SELECT * FROM LyShark;",db);     QSqlRecord rec = query.record();     // 循环所有记录     while(query.next())     {         // 判断当前记录是否有效         if(query.isValid())         {             int id_ptr = rec.indexOf("id");             int id_value = query.value(id_ptr).toInt();             int name_ptr = rec.indexOf("name");             QString name_value = query.value(name_ptr).toString();             int age_ptr = rec.indexOf("age");             int age_value = query.value(age_ptr).toInt();             std::cout << "ID: " << id_value << "Name: " << name_value.toStdString() << "Age: " << age_value << std::endl;         }     }     return true;}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    bool ref = SelectSQL();    std::cout << "select = > " << ref << std::endl;    return a.exec();}

循环输出的数据如下:

更新表中记录: 更新表中记录直接调用update语句即可,在调用之前通过QString sql拼接待修改语句并提交db.commit()事务即可完成更新.

#include <QCoreApplication>#include <QSqlDatabase>#include <QSqlError>#include <QSqlQuery>#include <QSqlRecord>#include <iostream>#include <QStringList>#include <QString>#include <QVariant>// 修改表中数据// https://www.cnblogs.com/lysharkbool UpdateSQL(QString uid, QString new_name){    // 指定数据库驱动类型    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("./lyshark.db");     if (!db.open())     {            std::cout << db.lastError().text().toStdString()<< std::endl;            return false;     }    // 执行SQL更新记录    QString sql = QString("update LyShark set name='%1' where id=%2;").arg(new_name).arg(uid);    db.exec(sql);    std::cout << "update => " << sql.toStdString() << std::endl;    // 提交事务请求    bool ref = db.commit();    db.close();    return true;}int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    // 更新ID=6的记录更新为 www.cnblogs.com/lyshark    bool ref = UpdateSQL("6","www.cnblogs.com/lyshark");    std::cout << "update flag: " << ref << std::endl;    return a.exec();}

更新后表中记录如下: