This statement is represented in the example as subquery S1.

这个语句在示例中表示为子查询s1。

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You cannot define a foreign key constraint in a CREATE TABLE statement that contains an AS subquery clause.

你不能在CREATE TABLE语句中包含A S子查询子句定义一个外键约束。

youdao

In the example, this is represented by the outermost select statement, which USES S1 as a subquery.

在这个示例中，这由最外层的选择语句表示，这个语句将S1用作子查询。

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