如何有效地使用 CASE 和 HAVING 子句来优化 SQL 服务器查询

Question

我有一个 SQL 查询，即

SELECT 
    A2P.aid,
    COUNT(*) [PaperCount],
    [2010] = SUM(CASE WHEN A2P.p_year = 2010 THEN 1 ELSE 0 END),
    [2011] = SUM(CASE WHEN A2P.p_year = 2011 THEN 1 ELSE 0 END),
    [2012] = SUM(CASE WHEN A2P.p_year = 2012 THEN 1 ELSE 0 END),
    [2013] = SUM(CASE WHEN A2P.p_year = 2013 THEN 1 ELSE 0 END),
    [2014] = SUM(CASE WHEN A2P.p_year = 2014 THEN 1 ELSE 0 END) 
FROM 
    sub_aminer_author2paper A2P
WHERE 
    aid IN (SELECT 
                aid 
            FROM 
                sub_aminer_author 
            WHERE 
                paper_count >= 20
           )
AND A2P.p_year BETWEEN 2010 AND 2014
GROUP BY 
    A2P.aid
HAVING 
    COUNT(DISTINCT A2P.pid) >= 2
ORDER BY 
    A2P.aid

现在，问题是我希望输出中的行在每列中包含 >= 2 的值，即 2010、2011、2012、2013，和 2014 OR 列中的值 Paper_Count >= 10 对于输出中的每一行。

此外，我使用的条件为：

HAVING 
        COUNT(DISTINCT A2P.pid) >= 2

但结果并不如人意。查看输出图像...

显然 0 值也在输出中检索到，这不是我们想要的。

请在这方面提供帮助。
谢谢！

Answer 1

查询您的Select您的条件：

Select A2P.aid, [PaperCount], [2010, [2011], [2012], [2013], [2014]
From (
    SELECT 
        A2P.aid,
        COUNT(*) [PaperCount],
        [2010] = SUM(CASE WHEN A2P.p_year = 2010 THEN 1 ELSE 0 END),
        [2011] = SUM(CASE WHEN A2P.p_year = 2011 THEN 1 ELSE 0 END),
        [2012] = SUM(CASE WHEN A2P.p_year = 2012 THEN 1 ELSE 0 END),
        [2013] = SUM(CASE WHEN A2P.p_year = 2013 THEN 1 ELSE 0 END),
        [2014] = SUM(CASE WHEN A2P.p_year = 2014 THEN 1 ELSE 0 END) 
    FROM 
        sub_aminer_author2paper A2P
    WHERE 
        aid IN (SELECT aid FROM sub_aminer_author WHERE paper_count >= 20)
    AND A2P.p_year BETWEEN 2010 AND 2014
    GROUP BY 
        A2P.aid
) x
Where [2010] >= 2 and [2011] >= 2 and [2012] >= 2 and [2013] >= 2 and [2014] >= 2;

或者像这样：

Select aid
    , [PaperCount] = [2010] + [2011] + [2012] + [2013] + [2014]
    , [2010], [2011], [2012], [2013], [2014]
From (
    SELECT aid, p_year
    FROM @sub_aminer_author2paper A2P
    WHERE aid IN (SELECT aid FROM @sub_aminer_author WHERE paper_count >= 20)
        AND p_year BETWEEN 2010 AND 2014
    GROUP BY A2P.aid, A2P.p_year
)p
Pivot (
    count(p_year)
    For p_year In ([2010], [2011], [2012], [2013], [2014])
) as piv
Where [2010] >= 2 and [2011] >= 2 and [2012] >= 2 and [2013] >= 2 and [2014] >= 2;

Answer 2

如果有人想看看我是如何实现的，我已经从不同的来源进行了编译并优化了我的查询。请看看这个。 https://junaidtechblog.wordpress.com/2019/09/04/optimize-sql-query-groupby-having/

如何有效地使用 CASE 和 HAVING 子句来优化 SQL 服务器查询

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