Ubuntu下Qt连接Mysql失败问题

代码：

    QSqlDatabase dbConn = QSqlDatabase::addDatabase("QMYSQL");
    dbConn.setHostName(m_hostName);
    dbConn.setDatabaseName(m_dbName);
    dbConn.setUserName(m_userName);
    dbConn.setPassword(m_password);

    if (!dbConn.open())
    {
        qDebug() << "open db failed:" << dbConn.lastError().text();
        return;
    }

    qDebug() << "open mysql...";

    dbConn.close();

使用Qt5.12.9开发，出现问题如下：

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7
open db failed: "Driver not loaded Driver not loaded"

分析：

available drivers中不包含QMYSQL，说明Qtxxx/xxx/gcc_64/plugins/sqldrivers下没有libqsqlmysql.so这个库，需要自己编译或者下载带这个库的Qt版本

现在安装Qt5.12.3版本，这个版本自带libqsqlmysql.so这个库

切换到Qt5.12.3版本后，运行代码，报错如下

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7
open db failed: "Driver not loaded Driver not loaded"

分析：

available drivers中包含QMYSQL，但依然出现 QMYSQL driver not loaded，说明 libqsqlmysql.so依赖可能有问题

# 到Qt安装目录
cd Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers

# 查看库依赖
ldd libqsqlmysql.so 

# 结果：
    linux-vdso.so.1 (0x00007ffd0f8a6000)
    libQt5Sql.so.5 => /home/dong/Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007fc40695f000)
    libQt5Core.so.5 => /home/dong/Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007fc4061cc000)
    libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fc406187000)
    libmysqlclient.so.18 => not found
    libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fc405fa6000)
    libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fc405e55000)
    libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fc405e3a000)
    libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fc405c48000)
    libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fc405c2c000)
    libicui18n.so.56 => /home/dong/Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.56 (0x00007fc405793000)
    libicuuc.so.56 => /home/dong/Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.56 (0x00007fc4053db000)
    libicudata.so.56 => /home/dong/Qt5.12.3/5.12.3/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.56 (0x00007fc4039f6000)
    libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fc4039f0000)
    libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007fc4039eb000)
    libglib-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fc4038c2000)
    /lib64/ld-linux-x86-64.so.2 (0x00007fc406dbc000)
    libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007fc40384f000)

可以看到 libmysqlclient.so.18 => not found

接下来安装libmysqlclient.so.18这个库即可

下载驱动

安装：

sudo dpkg -i libmysqlclient18_5.6.25-0ubuntu1_amd64.deb