Question

我将每年按性别创建一个人口图，图表如下图所示。

但是我对查询很难过。

查询

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结果

结果中，2016年男性人数为4人，女性人数为8人。2017年，我希望2017年的男性人数加上男性人数2017年，意味着2017年男性人数将为5人，与女性人数相同和总数。我在下面提供了一个结果应该是什么样子的图片。你能帮我解决这个问题，让我继续做图表吗？或者还有其他方法可以达到这个目的吗？

Answer 1

试试这个：

SELECT
    year_added,
    @malecount_v := @malecount_v + malecount as malecount,
    @femalecount_v := @femalecount_v + femalecount as femalecount,
    @totalcount_v := @totalcount_v + totalcount as totalcount
FROM (
    SELECT
       year_added,
       COUNT(case when gender='Male' then 1 end) as malecount,
       COUNT(case when gender='Female' then 1 end) as femalecount,
       COUNT(*) as totalcount
    FROM tbl
    WHERE status = 1
    GROUP BY year_added
    ORDER BY year_added
) t1
CROSS JOIN (SELECT @malecount_v := 0, @femalecount_v := 0, @totalcount_v := 0) t2

Answer 2

在Mysql中，您可以使用variables来完成，例如：

SELECT
     year_added,
     (@iMalecount := (COUNT(CASE WHEN gender = 'Male' THEN 1 END) + @iMalecount)) AS malecount,
     (@iFemalecount := (COUNT(CASE WHEN gender = 'Female' THEN 1 END) + @iFemalecount)) AS femalecount,
     (@iTotalcount := (COUNT(gender) + @iTotalcount)) AS totalcount
FROM tbl
WHERE status = 1
GROUP BY year_added

但不是100％，因为您可以在文档中阅读。

在其他SQL风格中，您可能需要一个存储过程。

Answer 3

你可以简单地使用

 WITH TableCount AS 
(
     SELECT
       year_added,
       COUNT(case when gender='Male' then 1 end) as malecount,
       COUNT(case when gender='Female' then 1 end) as femalecount,
       COUNT(*) as totalcount
  FROM tbl
  WHERE status = 1
  GROUP BY year_added
)

之后使用以下查询

    SELECT 
       SUM(malecount) as 'malecount',
       SUM(femalecount) as 'femalecount',
       SUM(totalcount) as 'totalcount'
    FROM TableCount

如果您使用MySql，可以使用临时表来执行类似CTE的操作

CREATE TEMPORARY TABLE IF NOT EXISTS TableCount AS (
SELECT
           year_added,
           COUNT(case when gender='Male' then 1 end) as malecount,
           COUNT(case when gender='Female' then 1 end) as femalecount,
           COUNT(*) as totalcount
      FROM tbl
      WHERE status = 1
      GROUP BY year_added
)

然后你可以使用上面的查询

 SELECT 
       SUM(malecount) as 'malecount',
       SUM(femalecount) as 'femalecount',
       SUM(totalcount) as 'totalcount'
    FROM TableCount

创建表时可以使用TEMPORARY关键字。临时的 table仅对当前会话可见，并被删除会话关闭时自动这意味着两个不同的会话可以使用相同的临时表名称相互冲突或与现有的非TEMPORARY表冲突同名。（现有表隐藏到临时表之前被删除。）要创建临时表，您必须具有CREATE TEMPORARY TABLES特权。

通过使用临时表概念，您可以在MySql中实现常见的表表达式功能

获取上一行中列的值，并添加到下一行的下一列

3 个答案: