轉自：http://blog.csdn.net/qq_28851503/article/details/52422302

首先貼上我遇到的問題,如下:

QSqlDatabase: QMYSQL driver not loaded

QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

Unable to open database

在解決這個問題的時候,首先在網上查詢了各種解決方案,都嘗試過,但是其中遇到的一些小問題,總是找不到解決方法,最終在"Stack Overflow"上提問得到了答案,故此記錄一下,一遍以後備用,也希望能幫助到一些人.

環境:   ubantu16.04 + Qt5.7 + MySql5.7

分析

2. 進入驅動所在目錄:

cd  /ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers

3. ls 檢視目錄裡面的檔案: 

[email protected]:~/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers$ ls
libqsqlite.so  libqsqlmysql.so  libqsqlpsql.so

4. 執行命令檢視 libqsqlmysql.so 的依賴:

ldd libqsqlmysql.so 

顯示如下:

1. linux-vdso.so.1 =>  (0x00007ffcb64e2000)  
2. libmysqlclient_r.so.16 => not found  
3. libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fea06463000)  
4. libcrypt.so.1 => /lib/x86_64-linux-gnu/libcrypt.so.1 (0x00007fea0622a000)  
5. libnsl.so.1 => /lib/x86_64-linux-gnu/libnsl.so.1 (0x00007fea06011000)  
6. libssl.so.10 => /usr/lib/x86_64-linux-gnu/libssl.so.10 (0x00007fea05dba000)  
7. libQt5Sql.so.5 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libQt5Sql.so.5 (0x00007fea05b74000)  
8. libQt5Core.so.5 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libQt5Core.so.5 (0x00007fea05459000)  
9. libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x00007fea0523c000)  
10. libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fea04eb9000)  
11. libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fea04bb0000)  
12. libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fea0499a000)  
13. libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fea045d0000)  
14. libnss3.so => /usr/lib/x86_64-linux-gnu/libnss3.so (0x00007fea0428a000)  
15. libnssutil3.so => /usr/lib/x86_64-linux-gnu/libnssutil3.so (0x00007fea0405d000)  
16. libplc4.so => /usr/lib/x86_64-linux-gnu/libplc4.so (0x00007fea03e57000)  
17. libnspr4.so => /usr/lib/x86_64-linux-gnu/libnspr4.so (0x00007fea03c18000)  
18. libicui18n.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicui18n.so.56 (0x00007fea0377d000)  
19. libicuuc.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicuuc.so.56 (0x00007fea033c5000)  
20. libicudata.so.56 => /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/plugins/sqldrivers/./../../lib/libicudata.so.56 (0x00007fea019e2000)  
21. libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fea017dd000)  
22. libgthread-2.0.so.0 => /usr/lib/x86_64-linux-gnu/libgthread-2.0.so.0 (0x00007fea015db000)  
23. librt.so.1 => /lib/x86_64-linux-gnu/librt.so.1 (0x00007fea013d3000)  
24. libglib-2.0.so.0 => /lib/x86_64-linux-gnu/libglib-2.0.so.0 (0x00007fea010c2000)  
25. /lib64/ld-linux-x86-64.so.2 (0x0000560757219000)  
26. libplds4.so => /usr/lib/x86_64-linux-gnu/libplds4.so (0x00007fea00ebd000)  
27. libpcre.so.3 => /lib/x86_64-linux-gnu/libpcre.so.3 (0x00007fea00c4d000)  

5.檢視自己所有的 libmysqlclient.so

[email protected]:~$ locate libmysqlclient.so

/home/cc/Desktop/libmysqlclient.so.20
/usr/lib/x86_64-Linux-gnu/libmysqlclient.so
/usr/lib/x86_64-linux-gnu/libmysqlclient.so.20
/usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.0

可知到我們的依賴有這些.

編譯MySql驅動

1.首先要確定自己在安裝Qt的時候安裝了原始碼,如果沒有安裝原始碼,則需要重灌Qt,切記裝的時候記得選上原始碼那一項.

2.進入到原始碼中MySQL驅動的原始碼中

cd /ProgramFiles/Qt5.7.0/5.7/Src/qtbase/src/plugins/sqldrivers/mysql

路徑是各自安裝qt的路徑而來.

3. 執行編譯:

qmake->make->make install

執行過程:

sudo /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/bin/qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient_r" mysql.pro

sudo make

sudo make install

在檢視依賴 ldd libqsqlmysql.so ,則會看到已有依賴庫.

再去執行程式,則會顯示成功連線資料庫.

Database connection established

這是記得要sudo make clean清理一下之前編譯的中間檔案.

可能出現的問題

1.執行qmake的時候: qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient_r" mysql.pro這樣的命令是用的預設的qmake檔案,這樣如果沒有Qt4的SDK,則會出錯,所以需要用我們自己安裝Qt時路勁下的qmake.

sudo /home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/bin/qmake "INCLUDEPATH+=/usr/include/mysql" "LIBS+=-L/usr/lib/mysql -lmysqlclient_r" mysql.pro

需要加上sudo,不然會出現 not permit的錯誤,即沒有許可權,所以需要用root許可權.

2.在執行make的時候,也需要用到root許可權.不然會出現以下錯誤:

注: 我本人就是死在這裡,因為沒有用root許可權,但是出現錯誤又不懂什麼原因,迷茫了2天,終於解決.

home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/bin/moc -DQT_NO_MTDEV -DQT_NO_LIBUDEV -DQT_NO_TSLIB -DQT_NO_LIBINPUT -DQT_NO_CAST_TO_ASCII -DQT_NO_CAST_FROM_ASCII -DQT_NO_EXCEPTIONS -D_LARGEFILE64_SOURCE -D_LARGEFILE_SOURCE -DQT_NO_DEBUG -DQT_PLUGIN -DQT_SQL_LIB -DQT_CORE_LIB -I/home/cc/ProgramFiles/Qt5.7.0/5.7/Src/qtbase/mkspecs/linux-g++ -I/home/cc/ProgramFiles/Qt5.7.0/5.7/Src/qtbase/src/plugins/sqldrivers/mysql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtSql/5.7.0 -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtSql/5.7.0/QtSql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtCore/5.7.0 -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtCore/5.7.0/QtCore -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtSql -I/home/cc/ProgramFiles/Qt5.7.0/5.7/gcc_64/include/QtCore -I/usr/include/c++/5 -I/usr/include/x86_64-linux-gnu/c++/5 -I/usr/include/c++/5/backward -I/usr/lib/gcc/x86_64-linux-gnu/5/include -I/usr/local/include -I/usr/lib/gcc/x86_64-linux-gnu/5/include-fixed -I/usr/include/x86_64-linux-gnu -I/usr/include main.cpp -o .moc/main.moc
moc: Cannot create .moc/main.moc
Makefile:652: recipe for target '.moc/main.moc' failed
make: *** [.moc/main.moc] Error 1

1. -lQt5Sql -lQt5Core -lpthread    
2. /usr/bin/ld: cannot find -lmysqlclient_r  
3. collect2: error: ld returned 1 exit status  
4. Makefile:114: recipe for target '../../../../plugins/sqldrivers/libqsqlmysql.so' failed  
5. make: *** [../../../../plugins/sqldrivers/libqsqlmysql.so] Error 1  

/home/cc/Desktop/libmysqlclient.so.20/usr/lib/x86_64-linux-gnu/libmysqlclient.so/usr/lib/x86_64-linux-gnu/libmysqlclient.so.20/usr/lib/x86_64-linux-gnu/libmysqlclient.so.20.3.0

所以要去連結出lmysqlclient_r相關的檔案;

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這樣在去執行sudo make命令,則會成功.

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注:

大家在用這個篇文章的時候若不能解決問題,也希望能在評論中給出,我們一起討論解決.

轉載請註明出處!

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