报错信息：An Apple ID with identifier “xxx”is not available. Please enter a different string.
原因：Bundle ID和别的冲突了（重复了，Bundle ID必须具有唯一性）
解决方法：单击最左侧导航栏里面的工程名 -》Identity -》修改Bundle Identifier
【iOS】Signing for requires a development team. Select a development team in the project editor. Code signing is required for product type ‘Application’ in SDK ‘iOS 10.0’
报错信息：Signing for “demo1_greating” requires a development team. Select a development team in the project editor.
Code signing is required for product type ‘Application’ in SDK ‘iOS 10.0’
解决方法：单击工程名 -》Signing -》 Team -》 选择对应的Account（如果没有Account，需要主动创建一个）
主动添加Account的方法请参考http://www.liuchuo.net/archives/284
【iOS】Could not launch Verify the Developer App certificate for your account is trusted on your device. Open Settings on iPhoneSE rational and navigate to General -> Device Management, then select your Developer App certificate to trust it.
报错信息为：Could not launch Verify the Developer App certificate for your account is trusted on your device. Open Settings on iPhoneSE rational and navigate to General -> Device Management, then select your Developer App certificate to trust it.
解决方法：手机（真机）中点击设置(Settings) -》 通用（General）-》设备管理（Device Management）-》点击对应的id -》信任（Trust）
【iOS】Unlock iPhone to Continue Xcode cannot launch demo1_greating on iPhone because the device is locked.
错误信息为：
Unlock iPhone to Continue
Xcode cannot launch demo1_greating on iPhone because the device is locked.
原因是手机使用USB连接后屏幕未解锁导致的。。。
【iOS】The run destination iPhone is not valid for Running the scheme .
错误信息如下：
The run destination iPhoneSE rational is not valid for Running the scheme ‘demo1_greating’.
iPhoneSE rational’s iOS 9.3.5 doesn’t match demo1_greating.app’s iOS 10.0 deployment target. Upgrade iPhoneSE rational’s iOS version or lower demo1_greating.app’s deployment target.
解决方法：这是因为运行设置的版本系统和真机的系统版本不匹配导致的，所以只需要单击工程文件，在出现的设置里面的Deployment info -》 Deployment Target中选择对应的真机的系统即可~
SQL命令向表中添加列
SQL语言用ALTER TABLE语句修改基本表，其一般格式为：
ALTER TABLE <表名>
[ADD [COLUMN] <新列名><数据类型>[完整性约束]]
[ADD <表级完整性约束>]
[DROP [COLUMN] <列名> [CASCADE | RESTRICT]]
[DROP CONSTRAINT<完整性约束名> [RESTRICT | CASCADE]]
[ALTER COLUMN <列名><数据类型>]
下面哪个SQL命令用来向表中添加列（ ）
A. MODIFY TABLE TableName ADD COLUMN ColumnName
B. MODIFY TABLE TableName ADD ColumnName
C. ALTER TABLE TableName ADD COLUMN ColumnName
D. ALTER TABLE TableName ADD ColumnName Type
【答案】：D
【解析】：由上面的语法格式可知排除A和B，修改列名的时候必须要指定数据类型，而C项没有指定列的数据类型，故这里选择D项