One such example is when the pushed down query is a common sub-expression.

一个例子就是被下推的查询是一个公共子表达式。

youdao

Notice that you can use the context directly in a sub-expression, without necessarily making it part of another expression. The result is.

请注意，您可以在子表达式中直接使用上下文，而无须使之成为另一个表达式的一部分。

youdao

Grouping is indicated by parentheses: any sub-expression contained in parentheses is treated as if it were atomic for the purpose of further grouping or repetition.

由括号表示分组：括号中包含的任何子表达式都被看作是用于以后分组或循环的原子。

youdao

x It says, take the name x and create a binding for that name to the value of the sub-expression and in fact to do this, to stress a point, let's do that.

它的意思是，创建了一个名字,然后创建了对于这个名字,和子表达式的值的绑定,实际上这么做，我们是为了，要强调一个点，让我们来说说这个点。

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