mysql - SQL 查询将记录分组在单独的字段下

Question

我正在使用 MySQL，我有以下架构:

id school          round score win loss tie
2  My School Name  1     10    1   0    0
3  My School Name  2     20    0   1    0
4  My School Name  3     30    1   0    0
5  My School Name  4     40    1   0    0
6  My School Name  5     50    1   0    0
7  My School Name  6     60    0   0    1

我需要以下输出，按学校名称分组

School         Round1 Round2 Round3 Round4 Round5 Round6 wins losses ties
My School Name 10     20     30     40     50     60     4    1      1

到目前为止，我觉得我可以使用 GROUP BY School 和 SUM(win) as wins 来获得它的大部分功能。不过，困难的部分是获取那些 Round_ 字段。

有人知道怎么做吗？在此先感谢，我们将不胜感激!

编辑:澄清一下，我知道我正好有 10 轮。

Answer 1

我们可以使用带有 GROUP BY 学校的 SELECT 语句为每所学校创建一条记录。如您所述，可以使用 SUM 聚合函数轻松计算领带、获胜和损失列。为了针对特定的回合，我们可以使用一些巧妙的数学运算(以避免像 CodeByMoonlight 建议的那样冗长的条件语句):

如果我们想以 R 轮为目标，我们注意到只有当 round == R 时“round-R”才为 0，否则它不是 0。当我们取“round-R”的 NOT 时，0 被反转为 1，而其他所有内容都设置为 0。现在，如果我们将 !(round-R) 乘以该回合的分数，当该回合不是 R(因为 0*score = 0)时，它会给我们 0当回合为 R 时会给我们“分数”(如 1*score = score)。接下来，当我们在列上取该值的 SUM 时，我们在 round=R 时添加分数，否则为 0，有效地只给我们轮 R 分数。

将所有这些放在一起给出:

SELECT school AS `School`,
SUM(!(round-1)*score) AS `Round1`,
SUM(!(round-2)*score) AS `Round2`,
SUM(!(round-3)*score) AS `Round3`,
SUM(!(round-4)*score) AS `Round4`,
SUM(!(round-5)*score) AS `Round5`,
SUM(!(round-6)*score) AS `Round6`,
SUM(!(round-7)*score) AS `Round7`,
SUM(!(round-8)*score) AS `Round8`,
SUM(!(round-9)*score) AS `Round9`,
SUM(!(round-10)*score) AS `Round10`,
SUM(win) AS `wins`,
SUM(loss) AS `losses`,
SUM(tie) AS `ties`
FROM `RoundScores` GROUP BY `school`

其中 RoundScores 是有问题的表。

编辑:

如果我们不想手动加10，我们可以使用prepared statements :

# Store all the conditionals in a string:
#   I was not able to to have round loop from 1 to 10, so I iterated over
#   all distinct values of 'round' present in the table.
SET @s =  "";
SELECT `round`, (@s := CONCAT( @s ,  "SUM(!(round-",round,  ")*score) AS `Round",round,  "`," )) FROM `RoundScores` GROUP BY `round`;

# Combine the conditionals from before with the rest of the statement needed.
SET @qry = CONCAT("SELECT school AS `School`,",@s,"SUM(win) AS `wins`,SUM(loss) AS `losses` FROM `RoundScores` GROUP BY `school`");

# Prepare and execute the statement.
PREPARE stmt1 FROM @qry;
EXECUTE stmt1;