QtCreator Qt中执行SQL语句,select,update,delete,insert

1 执行一个查询

发生错误后，QSqlQuery::exec()会返回false,错误信息在query.lastError()中

//创建数据库连接

if (!createConnection()) return 1;

QSqlDatabase db1 = QSqlDatabase::database("connection1");

//使用QSqlQuery查询整张表

QSqlQuery query1(db1);

qDebug() << "connection1:";

query1.exec("select * from student");

//显示错误信息

qDebug() << query1.lastError().text() ;

2 浏览结果集

query1.exec("select * from student");

while(query1.next()) {

qDebug() << query1.value("id").toInt() << "," << query1.value("name").toString();

}

QSqLQuery::value()可以返回当前记录的一个字段。返回一个QVariant,后面toInt(),toString()将其转换成相应类型

next()定位到下一条记录，

previous()前一条记录,

first()第一条纪律

last()定位到最后一条记录

seek(n)定位到第n条记录

at()返回当前行的索引

record()返回当前行的记录

size()返回总行数,通过QSqlDriver::hasFeature()判断是否支持

int numRows;

//判断是否支持QuerySize特性

if (db1.driver()->hasFeature(QSqlDriver::QuerySize)) {

qDebug() << "支持size()" << endl;

numRows = query1.size();

} else {

qDebug() << "不支持size()" << endl;

query1.last();

numRows = query1.at()+1;

}

query1.seek(2);    //指向索引为2的记录，即第3条记录

qDebug() << "当前记录:" <<query1.at() << endl;// 返回索引值

qDebug() << "id:" << query1.value(0).toInt() << ",name" << query1.value(1).toString();

qDebug() << "id:" << query1.value("id").toInt() << ",name:" << query1.value("name").toString();

QSqlRecord record = query1.record();//获取当前行的记录

//获取记录中"id"和"name"两个字段的值

qDebug() << "id:" << record.value("id").toInt() << ",name:" << record.value("name").toString();

//获取索引为1的字段，输出字段名与，值

QSqlField field = record.field(1);

qDebug() << "fieldName:" << field.name() << ",fieldValue:" << field.value().toString();

3 插入，更新和删除记录

Qt支持两种占位符：名称绑定和位置绑定

//名称绑定

query1.prepare("insert into student values(:id,:name)");

int idValue = 10;

QString nameValue = "ChenYun";

query1.bindValue(":id",idValue);

query1.bindValue(":name",nameValue);

qDebug() << query1.exec();

//位置绑定

query1.prepare("insert into student values(?,?)");

idValue = 20;

nameValue = "chenchen";

query1.addBindValue(idValue);

query1.addBindValue(nameValue);

query1.exec();

// 批处理

query2.prepare("insert into student (id, name) values (?, ?)");

QVariantList ids;

ids << 20 << 21 << 22;

query2.addBindValue(ids);

QVariantList names;

names << "xiaoming" << "xiaoliang" << "xiaogang";

query2.addBindValue(names);

if(!query2.execBatch()) qDebug() << query2.lastError();

// 更新

query2.exec("update student set name = 'xiaohong' where id = 20");

// 删除

query2.exec("delete from student where id = 21");

query2.exec("select * from student");

while(query2.next())

{

qDebug() << query2.value(0).toInt() << query2.value(1).toString();

}

4 事务

QSqlDatabase::transaction()//启动一个事务

QSqlDatabase::commit()//结束一个事务

QSqlDatabase::rollback()//数据回滚

tableModel->database().transaction();

if (tableModel->submitAll()) {

tableModel->database().commit();

} else {

tableModel->database().rollback();

QMessageBox::warning(this,"tableModel",QString("数据库错误:%1").arg(tableModel->lastError().text()));

}