Question

我有这个基本的sql查询，它获得“1级”的平均分数和总分数，并输出到csv文件

SELECT judge,AVG(score), count(judge) 
FROM results 
WHERE judge NOT LIKE '% AND %' 
  AND score >30 
  AND (class like '%1st%' OR class LIKE '%first%' OR class LIKE '%1 st%')
GROUP BY judge 
INTO OUTFILE 'c:/py/2013/all/judges-by-level.csv'
FIELDS TERMINATED BY ','
LINES TERMINATED BY '\r\n';

我想扩展此查询以从多个“级别”获得平均分数（从类列的字符串值派生）我当前的级别1 WHERE如下所示：
（class LIKE '%1st%' OR class LIKE '%first%' or class LIKE '%1 st%'）

我想使用类似的LIKE来更改此查询以获得级别2，级别3等（class LIKE '%2nd%' OR class LIKE '%second%' OR class LIKE '%2 nd%'）

原始数据如下：

judge   , score  ,class
John Doe, 55.123 ,First Level Championship
Jane Doe, 65.123 ,1st Amateur Division
John Doe, 75.123 ,Second Level Championship

我要输出的输出是一个格式如下的csv文件：

judge, level1_avg, level1_count, level2_avg, level2_count
John Doe,55.567,123,51.123,88
Jane Doe,58.123,66,53.123,247

我将使用哪种SQL语法来获得所需的输出？

Answer 1

您想基于first/1st/1 st和second/2nd/2 nd进行交叉制表吗？

作为一个侧面点，LIKE ... OR LIKE ... OR LIKE可以用正则表达式替换以缩短事物。

假设我正确地解答了你的问题，这应该接近你所需要的：

SELECT
  judge,
  AVG(case when class rlike '1st|first|1 st' THEN score END) level1_avg,
  COUNT(case when class rlike '1st|first|1 st' THEN judge END) level1_count,
  AVG(case when class rlike '2nd|second|2 nd' THEN score END) level2_avg,
  COUNT(case when class rlike '2nd|second|2 nd' THEN judge END) level2_count
FROM results
where judge not like '% and %' AND score > 30
group by judge
INTO OUTFILE 'c:/py/2013/all/judges-by-level.csv'
FIELDS TERMINATED BY ','
LINES TERMINATED BY '\r\n';

拆分level1_avg结果列：

如果class包含1st或first或1 st，则CASE会返回score，因此它会包含在平均值中。
如果class不包含1st或first或1 st，则CASE会返回null，因此不< / em>包含在平均值中。

其他聚合列使用类似的逻辑。

Answer 2

试试工会？虽然在这么多级别之后这不会有效。（注意INTO OUTFILE和ORDER BY在最后的联合条款中）

SELECT judge, AVG(score) as 'level1_avg', count(judge) as 'level1_count', '' as 'level2_avg', '' as 'level2_count', '' as 'level3_avg', '' as 'level3_count'  
FROM results 
WHERE judge NOT LIKE '% AND %' 
   AND score >30 
   AND (class like '%1st%' OR class LIKE '%first%' OR class LIKE '%1 st%')
GROUP BY judge

UNION ALL

SELECT judge, '' as 'level1_avg', '' as 'level1_count', AVG(score) as 'level2_avg', count(judge) as 'level2_count', '' as 'level3_avg', '' as 'level3_count'
FROM results 
WHERE judge NOT LIKE '% AND %' 
   AND score >30 
   AND (class like '%2nd%' OR class LIKE '%second%' OR class LIKE '%2 nd%')
GROUP BY judge    

UNION ALL

SELECT judge, '' as 'level1_avg', '' as 'level1_count', '' as 'level2_avg', '' as 'level2_count', AVG(score) as 'level3_avg', count(judge) as 'level3_count' 
   INTO OUTFILE 'c:/py/2013/all/judges-by-level.csv'
   FIELDS TERMINATED BY ','
   LINES TERMINATED BY '\r\n';
FROM results 
WHERE judge NOT LIKE '% AND %' 
   AND score >30 
   AND (class like '%3rd%' OR class LIKE '%third%' OR class LIKE '%3 rd%')
GROUP BY judge   
ORDER BY judge

编辑：在联盟的适当列中添加了空白

mysql-如何将简单选择转换为更复杂的查询

2 个答案: