SUM与支点来计算总得分

Question

从另一个问题，我得到这个查询来获取我的考试成绩总结了正确：

SELECT callSign,event, SUM(score) 
    FROM scores LEFT JOIN candidates 
ON scores.candidateID=candidates.id 
    WHERE candidateID IN 
    (SELECT id 
     FROM candidates 
    WHERE assessmentID='1321') 
    GROUP BY event, callSign 
    ORDER BY candidateID,event 

我得到那个看起来像数据：

callSign event   TotalScore 
Y209 Bridge     45 
Y209 PSA      3 
Y209 Team Analyst Exam  40 
X125 PSA      1 
X125 Team Analyst Exam  38 
V023 Amazing Race Planning 37 

我需要什么是数据，如：

callSign  Bridge PSA Amazing Race Planning  Team Analyst Exam 
V023        37 
Y209   45  3         40   
X125     1         38   

表结构

`events` 
id event 
1 PSA 
2 Bridge 
30 Stress Board 
25 Amazing Race Planning 
26 Amazing Race Execution 

`scores` 
id candidateID  event   rubric   category       score comment 
1 18  Team Analyst Exam Team Leader Rubric Organizes and Tasks Team Members 3  
2 18  Team Analyst Exam Team Leader Rubric Roles and Responsibilities   5  
3 18  Team Analyst Exam Team Leader Rubric Backward Planning     5  
4 18  Team Analyst Exam Team Leader Rubric Time Management 

`candidates`  
id firstName middleInitial lastName callSign service  rank sex  height weight assessmentID currentlyAssessing hired 

呼号就是X125会由于你正在使用MySQL，以透视数据成列去

Answer 1

，你将需要使用聚合函数与CASE表达：

SELECT callSign, 
    SUM(case when event = 'Bridge' then score else 0 end) as Bridge, 
    SUM(case when event = 'PSA' then score else 0 end) as PSA, 
    SUM(case when event = 'Amazing Race Planning' then score else 0 end) As AmazingRacePlanning, 
    SUM(case when event = 'Team Analyst Exam' then score else 0 end) as TeamAnalystExam 
FROM scores 
LEFT JOIN candidates 
    ON scores.candidateID=candidates.id 
WHERE candidateID IN (SELECT id 
         FROM candidates 
         WHERE assessmentID='1321') 
GROUP BY callSign 

如果你有数目不详的events，那么你将不得不使用准备好的语句来生成动态SQL：

SET @sql = NULL; 
SELECT 
    GROUP_CONCAT(DISTINCT 
    CONCAT(
     'sum(CASE WHEN event = ''', 
     event, 
     ''' THEN score END) AS `', 
     event, '`' 
    ) 
) INTO @sql 
FROM scores 
LEFT JOIN candidates 
    ON scores.candidateID=candidates.id; 


SET @sql 
    = CONCAT('SELECT callSign, ', @sql, ' 
      FROM scores 
      LEFT JOIN candidates 
       ON scores.candidateID=candidates.id 
      WHERE candidateID IN (SELECT id 
            FROM candidates 
            WHERE assessmentID=''1321'') 
      GROUP BY callSign'); 

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

编辑＃1，如果你的events都存储在一个单独的表，那么你可以使用以下方法来生成动态结果：

SET @sql = NULL; 
SELECT 
    GROUP_CONCAT(DISTINCT 
    CONCAT(
     'sum(CASE WHEN event = ''', 
     event, 
     ''' THEN score END) AS `', 
     event, '`' 
    ) 
) INTO @sql 
FROM events; 



SET @sql 
    = CONCAT('SELECT callSign, ', @sql, ' 
      FROM scores 
      LEFT JOIN candidates 
       ON scores.candidateID=candidates.id 
      WHERE candidateID IN (SELECT id 
            FROM candidates 
            WHERE assessmentID=''1321'') 
      GROUP BY callSign'); 

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

见SQL Fiddle with Demo