Once an application variable is bound to a parameter marker, the association remains until it is overridden or until the corresponding statement handle is freed.

一旦应用程序变量被绑定到某个参数标记，这种关联就会一直保持下去，直到相应的语句句柄被释放。

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If the remote data source cannot handle the null value in a host variable or parameter marker, any function that involves binding a nullable value has to be evaluated locally.

如果远程数据源不能处理主机变量或参数标记符中的NULL，那么任何需要绑定一个可以为空的值的函数都必须在本地计算。

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Here the document is provided as a literal value, but it could also be passed to the database through a parameter marker or host variable.

在这里，以字面值形式提供文档，但是也可以通过参数标志或主机变量把文档传递给数据库。

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