Query : select * from order LIMIT 0, 1000

Error Code : 1064

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'order LIMIT 0, 1000' at line 1
今天在查询数据的时候遇到这个错误，特别的郁闷，感觉自己写的sql语句没有问题啊，但就是提示我的sql语法错误，后来终于找到了原因


该错误一般出现在表名或字段名设计的过程中出现了mysql关键字导致的。


如果你用了mysql中的关键字做字段，当你查询的时候可以用  `order` 来括起来，这个 ` 并不是单引号，而是数字那一行键的最左边的那个键，在英文状态下的才为 ` ，用它把关键字括起来就可以解决这个问题。

Error Code：1093 是在执行DELETE或者UPDATE时含有子查询导致的。

You can't specify target table 'USER' from update in FROM clause

如：

UPDATE user SET usex = 4 WHERE

uage>(SELECT AVG(uage) FROM user);

可修改为：

UPDATE user SET usex = 4 WHERE

uage>(SELECT avg_uage FROM (SELECT AVG(uage) AS avg_uage FROM user) AS tmpuser);

Error Code：1248：

如果不在子查询后加别名AS tmpuser会报1248错误。

参考： MySQL更新时Error Code:1093和Error Code:1175的解决办法

      最近蓝牙手环在Android9.0的手机上回连总是连接不上，老在扫描的地方onScanFailed里回调errorCode=2，errorCode共有下面4种情况：

errorCode=1;Fails to start scan as BLE scan with the same settings is already started by the app.
errorCode=2;Fails to start scan as app cannot be registered.
errorCode=3;Fails to start scan due an internal error
errorCode=4;Fails to start power optimized scan as this feature is not supported

       发现BluetoothGatt.close()不管用，关闭重启手机蓝牙或者重启App是可以重新连接蓝牙，但是咱不能一碰到这个问题就让用户去重启App或者重启手机蓝牙。经过查阅各种资料，说问题的原因是：

       手机在startScan扫描的过程中还没来得及stopScan ,就被系统强制杀掉了, 导致mClientIf未被正常释放,实例和相关蓝牙对象已被残留到系统蓝牙服务中, 打开app后又重新初始化ScanCallback多次被注册,导致每次的扫描mClientIf的值都在递增, 于是mClientIf的值在增加到一定程度时(最大mClientIf数量视国产系统而定 不做深究),onScanFailed 返回了 errorCode =2  。

     解决办法是：重新刷新手机的蓝牙状态

    public static boolean releaseAllScanClient() {
        try {
            Object mIBluetoothManager = getIBluetoothManager(BluetoothAdapter.getDefaultAdapter());
            if (mIBluetoothManager == null) return false;
            Object iGatt = getIBluetoothGatt(mIBluetoothManager);
            if (iGatt == null) return false;

            Method unregisterClient = getDeclaredMethod(iGatt, "unregisterClient", int.class);
            Method stopScan;
            int type;
            try {
                type = 0;
                stopScan = getDeclaredMethod(iGatt, "stopScan", int.class, boolean.class);
            } catch (Exception e) {
                type = 1;
                stopScan = getDeclaredMethod(iGatt, "stopScan", int.class);
            }

            for (int mClientIf = 0; mClientIf <= 40; mClientIf++) {
                if (type == 0) {
                    try {
                        stopScan.invoke(iGatt, mClientIf, false);
                    } catch (Exception ignored) {
                    }
                }
                if (type == 1) {
                    try {
                        stopScan.invoke(iGatt, mClientIf);
                    } catch (Exception ignored) {
                    }
                }
                try {
                    unregisterClient.invoke(iGatt, mClientIf);
                } catch (Exception ignored) {
                }
            }
            stopScan.setAccessible(false);
            unregisterClient.setAccessible(false);
//            BLESupport.getDeclaredMethod(iGatt, "unregAll").invoke(iGatt);
            return true;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return false;
    }

@SuppressLint("PrivateApi")
    public static Object getIBluetoothGatt(Object mIBluetoothManager) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        Method getBluetoothGatt = getDeclaredMethod(mIBluetoothManager, "getBluetoothGatt");
        Object object=new Object();
        try {
            object=getBluetoothGatt.invoke(mIBluetoothManager);
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }
        return object;
    }


    @SuppressLint("PrivateApi")
    public static Object getIBluetoothManager(BluetoothAdapter adapter) throws NoSuchMethodException, IllegalAccessException, InvocationTargetException {
        Method getBluetoothManager = getDeclaredMethod(BluetoothAdapter.class, "getBluetoothManager");
        return getBluetoothManager.invoke(adapter);
    }


    public static Field getDeclaredField(Class<?> clazz, String name) throws NoSuchFieldException {
        Field declaredField = clazz.getDeclaredField(name);
        declaredField.setAccessible(true);
        return declaredField;
    }


    public static Method getDeclaredMethod(Class<?> clazz, String name, Class<?>... parameterTypes) throws NoSuchMethodException {
        Method declaredMethod = clazz.getDeclaredMethod(name, parameterTypes);
        declaredMethod.setAccessible(true);
        return declaredMethod;
    }


    public static Field getDeclaredField(Object obj, String name) throws NoSuchFieldException {
        Field declaredField = obj.getClass().getDeclaredField(name);
        declaredField.setAccessible(true);
        return declaredField;
    }


    public static Method getDeclaredMethod(Object obj, String name, Class<?>... parameterTypes) throws NoSuchMethodException {
        Method declaredMethod = obj.getClass().getDeclaredMethod(name, parameterTypes);
        declaredMethod.setAccessible(true);
        return declaredMethod;
    }

 

调用上面的反射还不行，因为Android9.0对SDK的反射会抛出异常，弹出下面的警告窗口：



所以需要在App初始化的时候调用下面的反射来关闭Android9.0的弹窗：

@SuppressLint("PrivateApi")
private void closeAndroidPDialog(){
    try {
        Class aClass = Class.forName("android.content.pm.PackageParser$Package");
        Constructor declaredConstructor = aClass.getDeclaredConstructor(String.class);
        declaredConstructor.setAccessible(true);
    } catch (Exception e) {
        e.printStackTrace();
    }
    try {
        Class cls = Class.forName("android.app.ActivityThread");
        Method declaredMethod = cls.getDeclaredMethod("currentActivityThread");
        declaredMethod.setAccessible(true);
        Object activityThread = declaredMethod.invoke(null);
        Field mHiddenApiWarningShown = cls.getDeclaredField("mHiddenApiWarningShown");
        mHiddenApiWarningShown.setAccessible(true);
        mHiddenApiWarningShown.setBoolean(activityThread, true);
    } catch (Exception e) {
        e.printStackTrace();
    }
}

看了一下log，
20 error code ELIFECYCLE

21 error errno 1

22 error html-web@1.0.0 dev: `node build/dev-server.js`

22 error Exit status 1

23 error Failed at the html-web@1.0.0 dev script.

23 error This is probably not a problem with npm. There is likely additional logging output above.

24 verbose exit [ 1, true ]



解决方案：
是node_modules的权限问题，尝试着改变了对应用户名的权限，成功。