Question

寻找有关如何最好地提取某些数据的建议。我需要做一些计算，但是按年和月拉数据来制作这样的表格。如果有一种方法可以让范围自动生成年份，那就更好了。

        2012    2013    2014
Jan     $243    $567    $890
Feb     $123    $456    $908
Mar     ...       ...
Apr
May

我可以按年，月份来获取数据，但是如您所知，如果没有一些中间件存储并迭代找到的集合，则不容易将其放入HTML表中。

我使用了以下查询，但该查询很接近但不准确。

select year(date_donated) as year, monthname(date_donated) as month, sum(amount_donated) as total_donations, count(date_donated) as count_donations from my_donations where (date_donated between "2012-01-01" and "2014-12-31") group by year(date_donated), month(date_donated) order by field(month, 'January','February','March','April','May','June','July','August','September','October','November','December')

Answer 1

首先，在客户端执行此操作要容易得多。

但是如果由于某种原因你还想在数据库端转移数据，你可以利用动态SQL。

如果您希望连续几年和几个月不管数据如何，您还需要某种计数（数字）表。例如。喜欢这个

CREATE VIEW tally AS
  SELECT 0 n UNION ALL SELECT 1  UNION ALL SELECT 2 UNION ALL 
  SELECT 3   UNION ALL SELECT 4  UNION ALL SELECT 5 UNION ALL 
  SELECT 6   UNION ALL SELECT 7  UNION ALL SELECT 8 UNION ALL 
  SELECT 9   UNION ALL SELECT 10 UNION ALL SELECT 11;

现在是动态SQL部分：

SET @sql = NULL;

SELECT GROUP_CONCAT(CONCAT('SUM(CASE WHEN YEAR(date_donated) = ', year_start + n, ' THEN amount_donated END) `', year_start + n, '`'))
  INTO @sql
  FROM tally CROSS JOIN (SELECT 2012 year_start, 2014 year_end) y
 WHERE n <= year_end - year_start 
 ORDER BY n;

SET @sql = CONCAT('SELECT MONTHNAME(''2000-01-01'' + INTERVAL n MONTH) month,', @sql,
' FROM tally t LEFT JOIN 
(
   SELECT date_donated, amount_donated
     FROM my_donations
    WHERE date_donated BETWEEN ''', 2012, '-01-01'' AND ''', 2014, '-12-31'' 
) d
  ON t.n + 1 = MONTH(date_donated)                
GROUP BY t.n 
ORDER BY t.n');

PREPARE stmt FROM @sql;
EXECUTE stmt;
DEALLOCATE PREPARE stmt;

输出：

|     MONTH |   2012 |   2013 |   2014 |
|-----------|--------|--------|--------|
|   January |    243 |    567 |    890 |
|  February |    123 |    456 |    908 |
|     March | (null) | (null) | (null) |
...

这是 SQLFiddle 演示

按年份列和月份的MySQL总计

1 个答案: