SQL：输出顺序
我正在检查 postgresql 的文档以了解递归查询，其中有一个示例。
WITH RECURSIVE t(n) AS (
VALUES (1)
UNION ALL
SELECT n+1 FROM t WHERE n < 100
)
SELECT sum(n) FROM t
上面的语句和100条SELECT语句一样吗？来自文档：
递归查询通常用于处理分层或树结构数据。
如果我想根据某些条件对分层结构进行排序，建议使用递归查询。例如。 SQL 查询：从表中获取有序行 - II 以及接受的答案。是否应该从数据库检索数据，然后在内存中排序。或者RECURSIVE查询会更加高效！！
I was checking the docs of postgresql for Recursive queries where I got an example.
WITH RECURSIVE t(n) AS (
VALUES (1)
UNION ALL
SELECT n+1 FROM t WHERE n < 100
)
SELECT sum(n) FROM t
Is the above statement same as 100 SELECT statements. From the docs:
Recursive queries are typically used to deal with hierarchical or tree-structured data.
If I want to sort the hierarchical structure based on some criteria will it be advisable to recursive query. eg. SQL Query: Fetch ordered rows from a table - II and the accepted answer. Should the data be retrieved from the DB and then sorted in memory. Or RECURSIVE query will be more effcient !!
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答案取决于您的架构设计、硬件/操作系统、配置和加载的数据量。使用解释和解释分析两种方式运行它，并从几个典型查询中选择最快的。
即使我有足够的信息来猜测您的模式和示例数据，任何对我有利的答案可能对您不利。
The answer depends on your schema design, hardware/OS, configuration, and volume of data loaded. Run it both ways with explain and explain analyze and pick the fastest over several typical queries.
Even if I had enough information to guess your schema and exemplar data, any answer good for me may not the good for yo.