如何在 SQL 中的列内聚合值？

Question

我无法解决这个问题，有什么帮助吗？

Batsman_detail 表有列， [反对（varchar），运行（int），解雇（varchar），场地（varchar）]：

• opposition 列中包含多个国家/地区。

• runs 栏显示击球手在那场比赛中的得分。

• dimissal 列具有以下任何值被捕获/保住/用完/未用完。

• venue 列包含举行比赛的体育场名称。

现在您应该编写一个查询，以便输出表必须包含击球手在针对巴基斯坦、澳大利亚和斯里兰卡的国家被解雇的次数（原始表包含许多国家。），

示例输出格式：

opposition                caught     bowled      runout      notout    
Pakistan                  3              5               7               9   
Australia                 0              4               4               1    
Sri Lanka                 4              2               3               4

Answer 1

你似乎想要条件聚合：

select opposition,
    sum(case when dismissal = 'caught'  then runs else 0 end) caught,
    sum(case when dismissal = 'bowled'  then runs else 0 end) bowled,
    sum(case when dismissal = 'run out' then runs else 0 end) run_out,
    sum(case when dismissal = 'not out' then runs else 0 end) not_out
from batsman
group by opposition

这对dismissal 的每个值求和runs。如果你只想统计出现次数，那么：

select opposition,
    sum(dismissal = 'caught')  caught,
    sum(dismissal = 'bowled')  bowled,
    sum(dismissal = 'run out') run_out,
    sum(dismissal = 'not out') not_out
from batsman
group by opposition

Answer 2

您可以清楚地选择所有解雇案例，然后动态旋转

SET @sql = NULL;

SELECT GROUP_CONCAT(
             CONCAT(
                    'SUM(CASE WHEN dismissal =''', dismissal, ''' THEN runs ELSE 0 END ) AS ',
                     dismissal
                    )
       )
  INTO @sql
  FROM ( SELECT DISTINCT dismissal
           FROM Batsman_detail 
       ) b;

SET @sql = CONCAT('SELECT opposition,',@sql,
                   ' FROM Batsman_detail
                    GROUP BY opposition'); 


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

Demo