一些函数的输入是数值，比如字符串函数的起始、长度和偏移量参数。

For some functions, a numeric value is input, for example start, length, and offset parameters of string functions.

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它不会对数值字段生效，除非这些字段具有一致的长度。

It does not work on numeric fields unless the fields are all the same length.

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字符串长度单元属于数值。

The string length unit pertains to the numeric values.

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You're going to get a chance to explore them, and you'll see not only are there the standard numerics for strings, there are things like length or plus or other things you can do with them.

以后你们还会学到更多，你会学到字符串,不仅仅能运用标准数值运算，你还可以对他们求长度,或者加上其他的东西。

麻省理工公开课 - 计算机科学及编程导论课程节选