为了解决嵌套结构转换的难点，引进了查询块的概念，实现了查询块向SQL语句转换的算法，并将此转换方法与以前的方法进行了比较。

In order to solve the difficulty of nested structure of SQL, the idea of query block is introduced and the algorithm of changing query block to SQL is realized.

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块语句减少了当控制结构嵌套时候可能引起的混淆，提供了一种提高代码可读性的组织机制。

Block statements reduce the ambiguity that often arises when control constructs are nested, and they provide a mechanism for organizing the code for improved readability.

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