Question

我怎么能查询，就像我想要输出一样，就像我用tbl_clinics.clinic_name对它进行分组。现在我的查询发生了什么？它为什么，它没有显示我的零值，就像我想要这样的输出：

clinic name | total_check
 Clinic 1   |    4
 Clinic 2   |    0
 Clinic 3   |    0
 Clinic 4   |    0

这是我的问题：

SELECT
tbl_clinics.clinic_name,
COALESCE(COUNT(tbl_check_up.check_up_id),0) AS total_check
FROM
tbl_clinics
LEFT OUTER JOIN tbl_check_up ON tbl_clinics.clinic_id = tbl_check_up.clinic_id
WHERE tbl_clinics.user_id = "102" AND MONTH(tbl_check_up.check_up_date) = "02"  
GROUP BY tbl_clinics.clinic_name

我得到的只是这些：

   clinic_name   |   total_check
    Clinic 1     |      4

为什么它没有显示我的其他诊所？ ..我怎么能操纵这些？。请帮助我从我想要的产品中获得正确的输出，并向我解释为什么我的输出不是很好。

Answer 1

WHERE子句将确定将输出哪些行。如果您希望输出表“tbl_clinics”中的所有记录，请尝试以下操作：

SELECT tbl_clinics.clinic_name,
       Count(tbl_check_up.check_up_id) AS total_check
FROM   tbl_clinics
       LEFT JOIN tbl_check_up
              ON tbl_clinics.clinic_id = tbl_check_up.clinic_id
                 AND tbl_clinics.user_id = "102"
                 AND Month(tbl_check_up.check_up_date) = "02"
GROUP  BY tbl_clinics.clinic_name

另外，我认为COUNT（）上的COALESCE（）是不必要的，因为当没有遇到行时，COUNT（）将始终返回0，而不是NULL。

Answer 2

你可以尝试

<?xml version="1.0"?>
<manifest package="net.geographx.LinesGame" xmlns:android="http://schemas.android.com/apk/res/android" android:versionName="1.0" android:versionCode="10" android:installLocation="auto">
    <application android:hardwareAccelerated="true" android:name="org.qtproject.qt5.android.bindings.QtApplication" android:label="@string/app_name" android:icon="@drawable/icon">
        <activity android:configChanges="orientation|uiMode|screenLayout|screenSize|smallestScreenSize|layoutDirection|locale|fontScale|keyboard|keyboardHidden|navigation" android:name="org.qtproject.qt5.android.bindings.QtActivity" android:label="@string/app_name" android:screenOrientation="portrait" android:launchMode="singleTop">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER"/>
            </intent-filter>

            <!-- Application arguments -->
            <!-- meta-data android:name="android.app.arguments" android:value="arg1 arg2 arg3"/ -->
            <!-- Application arguments -->

            <meta-data android:name="android.app.lib_name" android:value="LinesGameQt"/>
            <meta-data android:name="android.app.qt_sources_resource_id" android:resource="@array/qt_sources"/>
            <meta-data android:name="android.app.repository" android:value="default"/>
            <meta-data android:name="android.app.qt_libs_resource_id" android:resource="@array/qt_libs"/>
            <meta-data android:name="android.app.bundled_libs_resource_id" android:resource="@array/bundled_libs"/>
            <!-- Deploy Qt libs as part of package -->
            <meta-data android:name="android.app.bundle_local_qt_libs" android:value="1"/>
            <meta-data android:name="android.app.bundled_in_lib_resource_id" android:resource="@array/bundled_in_lib"/>
            <meta-data android:name="android.app.bundled_in_assets_resource_id" android:resource="@array/bundled_in_assets"/>
            <!-- Run with local libs -->
            <meta-data android:name="android.app.use_local_qt_libs" android:value="1"/>
            <meta-data android:name="android.app.libs_prefix" android:value="/data/local/tmp/qt/"/>
            <meta-data android:name="android.app.load_local_libs" android:value="plugins/platforms/android/libqtforandroid.so:plugins/bearer/libqandroidbearer.so:lib/libQt5QuickParticles.so:plugins/mediaservice/libqtmedia_android.so:lib/libQt5MultimediaQuick_p.so"/>
            <meta-data android:name="android.app.load_local_jars" android:value="jar/QtAndroid.jar:jar/QtAndroid-bundled.jar:jar/QtAndroidBearer.jar:jar/QtAndroidBearer-bundled.jar:jar/QtMultimedia.jar:jar/QtMultimedia-bundled.jar"/>
            <meta-data android:name="android.app.static_init_classes" android:value="org.qtproject.qt5.android.multimedia.QtMultimediaUtils:org.qtproject.qt5.android.multimedia.QtMultimediaUtils"/>
            <!--  Messages maps -->
            <meta-data android:value="@string/ministro_not_found_msg" android:name="android.app.ministro_not_found_msg"/>
            <meta-data android:value="@string/ministro_needed_msg" android:name="android.app.ministro_needed_msg"/>
            <meta-data android:value="@string/fatal_error_msg" android:name="android.app.fatal_error_msg"/>
            <!--  Messages maps -->

            <!-- Splash screen -->
            <!-- meta-data android:name="android.app.splash_screen_drawable" android:resource="@drawable/logo"/ -->
            <!-- meta-data android:name="android.app.splash_screen_sticky" android:value="true"/ -->
            <!-- Splash screen -->

            <!-- Background running -->
            <!-- Warning: changing this value to true may cause unexpected crashes if the
                          application still try to draw after
                          "applicationStateChanged(Qt::ApplicationSuspended)"
                          signal is sent! -->
            <meta-data android:name="android.app.background_running" android:value="false"/>
            <!-- Background running -->

            <!-- auto screen scale factor -->
            <meta-data android:name="android.app.auto_screen_scale_factor" android:value="false"/>
            <!-- auto screen scale factor -->

            <!-- extract android style -->
            <!-- available android:values :
                * full - useful QWidget & Quick Controls 1 apps
                * minimal - useful for Quick Controls 2 apps, it is much faster than "full"
                * none - useful for apps that don't use any of the above Qt modules
                -->
            <meta-data android:name="android.app.extract_android_style" android:value="full"/>
            <!-- extract android style -->
    </activity>

    <!-- For adding service(s) please check: https://wiki.qt.io/AndroidServices -->

    </application>

    <uses-sdk android:minSdkVersion="19" android:targetSdkVersion="23"/>
    <supports-screens android:largeScreens="true" android:normalScreens="true" android:anyDensity="true" android:smallScreens="true"/>

    <!-- OpenGL ES 3.0 - This API specification is supported by Android 4.3 (API level 18) and higher.  -->
    <uses-feature android:glEsVersion="0x00030000" android:required="true"/>

</manifest>

mysql查询在查询中显示为空

2 个答案: