Accidentally overwriting bindings by introducing a variable name that was previously defined in a macro.

如果引入的变量名正好是一个宏中以前定义过的，那么就会覆盖绑定。

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Define a database variable initially within the macro to tell it which database to connect to.

在宏内开头定义DATABASE变量告诉它要连接到哪一个数据库。

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For example, let's say that you wanted to create a macro that introduced a variable into a scope that could be used by the person calling the macro.

例如，假设您希望创建一个宏，它将一个变量引入调用宏的人可以使用的范围中。

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