簡述：
常用的數據庫操作主要有查詢、插入、刪除等
QSqlDatabase創建連接數據庫實例，一個QSqlDatabase的實例代表一個數據庫的連接。
Qt 提供了對不同數據庫的驅動支持：
| Driver Type | Description |
| QDB2 | IBM DB2 |
| QIBASE | Borland InterBase Driver |
| QMYSQL | MySQL Driver |
| QOCI | Oracle Call Interface Driver |
| QODBC | ODBC Driver (includes Microsoft SQL Server) |
| QPSQL | PostgreSQL Driver |
| QSQLITE | SQLite version 3 or above |
| QSQLITE2 | SQLite version 2 |
| QTDS | Sybase Adaptive Server |
1、創建連接數據庫
/**
* @brief initDb
* 創建Db
* @return
*/
bool initDb()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE", "project");
db.setHostName("localhost"); //數據庫主機名
db.setDatabaseName("myDb"); //數據庫名
db.setUserName("hebbe"); //數據庫用戶名
db.setPassword("123456"); //數據庫密碼
//db.open(); //打開數據庫連接 調用 open() 方法打開數據庫物理連接。在打開連接之前，連接不可用
//db.close(); //釋放數據庫連接
// create connection
if (!db.open())
{
qDebug() << "Sqlite open fail" << endl;
return false;
}
return true;
}
2、創建表
/**
* @brief createTable
* 創建表
* @return
*/
bool createTable()
{
QSqlQuery query(db);
QString cmd,cmd2;
quint16 num;
QString info, msg, info_other, msg_other;
QStringList list;
cmd = QString("CREATE TABLE IF NOT EXISTS tb_Error ("
"ErrorNo INTEGER NOT NULL PRIMARY KEY,"
"ErrorDetaInfo VARCHAR(255) NULL,"
"ErrorDetaInfo_En VARCHAR(255) NULL,"
"ErrorMesages VARCHAR(255) NULL,"
"ErrorMesages_En VARCHAR(255) NULL);"
);
if(!query.exec(cmd))
{
qDebug()<<"init tb_error errot"<<query.lastError();
}
if(query.exec("select count(1) from tb_Error"))
{
if(query.next())
{
if(query.value(0).toInt() == 0)
{
// 讀取錯誤信息插入數據庫
QFile file("./error.ini");
if(!file.open(QIODevice::ReadOnly))
{
}
QTextStream stream(&file);
QString line;
do
{
list.clear();
line = stream.readLine();
list = line.split("|");
if(list.count() == 5)
{
num = list.at(0).toUInt();
info = list.at(1);
msg = list.at(2);
info_other = list.at(3);
msg_other = list.at(4);
qDebug()<<"num = "<<num<<"info = "<<info<<"msg = "<<msg;
cmd2 = QString("INSERT INTO tb_Error(ErrorNo,ErrorDetaInfo,ErrorMesages,ErrorDetaInfo_En,ErrorMesages_En)VALUES(%1, \"%2\", \"%3\", \"%4\", \"%5\")")
.arg(num).arg(info).arg(msg).arg(info_other).arg(msg_other);
if(!query.exec(cmd2))
{
qDebug()<<"num = "<<num<<"info = "<<info<<"msg = "<<msg;
qDebug()<<"initError = "<<query.lastError();
// return false;
}
}
// qDebug()<<"inser to database msg"<<line;
}
while(!line.isNull());
file.close();
}
}
}
return true;
}
3、獲取列
/**
* @brief getColumn
* 獲取列
* @return
*/
int getColumn(const QString &tableName，QString item, QString itemStr)
{
QSqlQuery query(db);
QString sql;
sql = QString("select * from %1 WHERE %2 = '%3' ").arg(tableName).arg(item).arg(itemStr);
query.prepare(sql);
if(query.exec(sql))
{
QSqlRecord sqlRecord = query.record();
return sqlRecord.count();
}
else
{
qDebug()<<"get data failure:"<<query.lastError()<<"\n"<<sql;
}
return 0;
}
4、獲取行
/**
* @brief getRow
* 獲取列
* @return
*/
int getRow(const QString &tableName，QString item, QString itemStr)
{
QSqlQuery query(db);
QString sql;
sql = QString("select COUNT() from %1 ").arg(tableName);
query.prepare(sql);
if(query.exec(sql))
{
return query.value(0).toInt() ;
}
else
{
qDebug()<<"get data failure:"<<query.lastError()<<"\n"<<sql;
}
return 0;
}
5、獲取最大值
/**
* @brief getMaxDateTime
* 獲取列
* @return
*/
QDateTime getMaxDateTime(const QString &tableName)
{
QSqlQuery query(db);
QString sql;
sql = QString("select MAX(DateTime) from %1 ").arg(tableName);
query.prepare(sql);
if(query.exec(sql))
{
return query.value(0).toDateTime();
}
else
{
qDebug()<<"get data failure:"<<query.lastError()<<"\n"<<sql;
return QDateTime::currentDateTime();
}
}
6、獲取最小值
/**
* @brief getMinDateTime
* 獲取列
* @return
*/
QDateTime getMinDateTime(const QString &tableName)
{
QSqlQuery query(db);
QString sql;
sql = QString("select MIN(DateTime) from %1 ").arg(tableName);
query.prepare(sql);
if(query.exec(sql))
{
return query.value(0).toDateTime();
}
else
{
qDebug()<<"get data failure:"<<query.lastError()<<"\n"<<sql;
return QDateTime::currentDateTime();
}
}
7、查詢所有記錄
/**
* @brief selectAllData
* 獲取所有數據
* @return
*/
void selectAllData(const QString &tableName)
{
QSqlQuery query = QSqlQuery(db);
QString sql;
sql = QString("select * from %1 ").arg(tableName);
query.prepare(sql);
query.exec();
while (query.next()) //依次取出查詢結果的每一條記錄，直至結束
{
qDebug()<<query.value(0).toInt();
qDebug()<<query.value(1).toString();
}
}
8、獲取數據並分頁顯示到QTableView
int total; //總記錄數
int pageSize; //每頁顯示條數
int totalPage; //總頁數
int startPage; //起始頁
QSqlQueryModel *sqlQueryModel;
#define PAGE_SIZE 50
void init()
{
sqlQueryModel = new QSqlQueryModel(this);
QSqlQuery query(db);
ui->tableView->setModel(sqlQueryModel);
pageSize = PAGE_SIZE;
query.exec(QString("SELECT COUNT() FROM tb_Diagnose"));
while(query.next())
{
total = query.value(0).toInt();
}
if(total <= PAGE_SIZE)
totalPage = 1;
else
totalPage = (total%pageSize == 0)? (total/pageSize):(total/pageSize+1);
if(startPage > totalPage)
{
startPage = totalPage;
}
}
/**
* @brief selectAndShowData
* 從數據庫獲取數據，並在QTableView顯示
*
* @return
*/
void selectAndShowData()
{
QSqlQuery query(db);
QString cmd;
if(startPage < totalPage) {
cmd = QString("SELECT * FROM ( SELECT * FROM table limit %3, %4 ) a ORDER BY DateTime DESC ")
.arg(total-(startPage*pageSize)).arg(pageSize);
} else if(startPage == totalPage) {
cmd = QString("SELECT * FROM ( SELECT * FROM table limit 0, %3 ) a ORDER BY DateTime DESC ")
.arg(total-(startPage-1)*pageSize);
}
if(!query.exec(cmd))
{
qDebug()<<query.lastError();
}
sqlQueryModel->setQuery(query);
while(sqlQueryModel->canFetchMore())
sqlQueryModel->fetchMore();
ui->labelTitle->setText(tr("Log"));
ui->labelFooter->setText(tr("Page: %1/%2").arg(startPage).arg(totalPage));
sqlQueryModel->setHeaderData(0, Qt::Horizontal, tr("No."));
sqlQueryModel->setHeaderData(1, Qt::Horizontal, tr("ID"));
sqlQueryModel->setHeaderData(2, Qt::Horizontal, tr("Name"));
sqlQueryModel->setHeaderData(3, Qt::Horizontal, tr("Date/time"));
sqlQueryModel->setHeaderData(4, Qt::Horizontal, tr("Details"));
ui->tableView->setColumnWidth(0, 55);
ui->tableView->setColumnWidth(1, 150);
ui->tableView->setColumnWidth(2, 100);
ui->tableView->setColumnWidth(3, 255);
ui->tableView->setColumnWidth(4, ui->tableView->width()-55-100-150-255-ui->tableView->verticalScrollBar()->width());
}
9、插入數據
/**
* @brief insertData
* 插入數據
* @return
*/
bool insertData(QSqlQuery &query, quint64 rcNum, QString operatorId, QString describeStr)
{
QString cmd;
cmd = QString("INSERT INTO table(RcNum, DateTime, OperatorID, Operation) VALUES(%1, datetime('now'), '%2', \"%3\") ")
.arg(rcNum)
.arg(operatorId)
.arg(describeStr);
if(!query.exec(cmd))
{
qDebug()<<"INSERT table Error:"<<query.lastError()<<endl<<cmd;
return false;
}
else
return true;
}
10、更新數據
/**
* @brief updateData
* 更新數據
* @return
*/
bool updateData(QSqlQuery &query, quint64 rcNum, QString describeStr)
{
QString cmd;
cmd = QString("update table set Operation = '%1' where RcNum = %2")
.arg(describeStr)
.arg(rcNum);
if(!query.exec(cmd))
{
qDebug()<<"update table Error:"<<query.lastError()<<endl<<cmd;
return false;
}
else
return true;
}
11、刪除
/**
* @brief deleteData
* 刪除數據
* @return
*/
bool deleteData(QSqlQuery &query, quint64 rcNum)
{
QString cmd;
cmd = QString("delete from table where where RcNum = %1")
.arg(rcNum);
if(!query.exec(cmd))
{
qDebug()<<"delete table Error:"<<query.lastError()<<endl<<cmd;
return false;
}
else
return true;
}
/**
* @brief deleteAllData
* 刪除所有數據
* @return
*/
bool deleteAllData(QSqlQuery &query)
{
QString cmd;
cmd = QString("delete from table");
if(!query.exec(cmd))
{
qDebug()<<"delete table Error:"<<query.lastError()<<endl<<cmd;
return false;
}
else
return true;
}