如果 IN 列表中包含参数标记符或主机变量，使优化器不能使用编目统计信息来确定选择性，就会出现这种情况。
This can occur if the IN list contains parameter markers or host variables which prevent the optimizer from using catalog statistics to determine the selectivity.
不能使用这项功能将标准套件升级到最新的版本，无论这些版本是什么，这一限制使系统在网络环境中的使用变得更复杂。
You can't use the feature to upgrade a standard suite up to the latest versions -- whatever they may be -- and this stipulation makes the system complex to use in a network environment.
由此带来的优势就是使病毒注入几乎不可能，而作为代价，动态链接库和元编程技巧就不能使用了。
This has the advantage of making virus injection virtually impossible, at the cost of not being able to use dynamic link libraries or meta-programming techniques.
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