替代 SQL 查询答案

【问题标题】：Alternative SQL queries替代 SQL 查询
【发布时间】：2022-08-14 18:45:35
【问题描述】：

我需要三个替代查询返回与以下查询相同的答案。

SELECT building, SUM(budget) AS totalbudget
FROM department 
GROUP BY building
HAVING SUM(budget) > 10000;

创建三种替代方法以获得相同的确切结果，消除HAVING 子句。并为每个替代解释查询对性能的影响？

第一种方式：

SELECT building, totalbudget
FROM 
    (SELECT building, SUM(budget) AS totalbudget
     FROM department 
     GROUP BY building)
WHERE totalbudget > 10000;

还有另外两种方法...

您使用的是哪个 dbms？（不同的产品有不同的优化技巧。）
我的意思是，我在没有子句的情况下要求对该查询进行不同的查询。我使用甲骨文
是的，但你也写了\"对于每个备选方案，解释查询对性能的影响\"。
你问？你的意思是说这不是作业或面试问题吗？
其实这是一道考试题。这是不允许的吗？？？。但这是个好问题。

标签： sql oracle group-by having

【解决方案1】：

选项1：

SELECT *
FROM   department
MATCH_RECOGNIZE(
  PARTITION BY building
  MEASURES
    SUM(budget) AS totalBudget
  PATTERN (^ all_rows+ $)
  DEFINE
    all_rows AS 1 = 1
)
WHERE totalBudget > 10000

选项 2：

SELECT building,
       SUM(budget) AS totalbudget
FROM   department d
WHERE  10000 < (
  SELECT SUM(budget)
  FROM   department t
  WHERE  d.building = t.building
)
GROUP BY building

选项 3：

SELECT building,
       SUM(budget) AS totalbudget
FROM   department
GROUP BY building
ORDER BY totalbudget DESC
FETCH FIRST ( SELECT COUNT(*)
              FROM   (
                SELECT SUM(budget) AS total
                FROM   department
                GROUP BY building
              )
              WHERE total > 10000            ) ROWS ONLY;

并为每个替代解释查询对性能的影响？

它们的性能都会比使用HAVING 更差。

db<>小提琴here

【讨论】：