MySQL类型转换注意事项_MySQL
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最近在做的一项工作是将之前使用MSSQLServer数据库的服务，
改写为支持MySQL数据库，SQL语句中涉及了一些类型转换的功能，
结果发现MySQL的类型转换函数“CONVERT”并没有提供很好的数据类型名称的兼容性，
参数顺序上也不一样！
SQLServer中使用convert(int, Port)，MySQL中要使用convert(Port, SIGNED) AS `port`
注意：如果不加AS `port`结果集中列名就会显示成convert(Port, SIGNED)
SQLServer中使用中括号[]解决特殊符号、关键字等问题，但MySQL中需要使用反单引号
俗称小句号，上句号，也称重音符，就是键盘左上角Esc下面那么键，输入时不按Shift。
转换时使用的数据类型需要注意，这个类型 可以是以下值其中的 一个：
BINARY[(N)]
CHAR[(N)]
DATE
DATETIME
DECIMAL
SIGNED [INTEGER]
TIME
UNSIGNED [INTEGER]
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