獲取不同值的總計數

Question

我有一個包含3個字段的品牌，型號和BenchMark分數的MySQL表。

有關數據如何在此表中的注意事項。

1.品牌可以有不同的型號。 2.不同的品牌可以有同樣的型號 3.特定品牌型號組合可以有不同的Benchmark分數。

所以表中的數據將是這個樣子

Brand ModelName Benchmark 

B1 M1   1000 
B1 M1   2000 
B1 M2   3000 
B1 M2   2000 
B2 M1   3000 
B2 M3   4000 

現在我需要的是找到的時間數量的特定基準分數報告。

在這裏，我們應該只計算那些模型 - 品牌組合的最大基準分數，而不是所有這些基準分數。

結果應該是這樣的

Score Times 
3000 2 
2000 1 
4000 1 

那麼應該是MySQL的聲明，如果我需要這個result..please幫助

Answer 1

SELECT * FROM 
(SELECT MX,COUNT(1) SC FROM 
(SELECT MAX(MaxScores.MaxScore) MX,ScoreCounts.ScoreCount FROM 
(
    SELECT MAX(BenchMark) MaxScore,Brand,ModelName 
    FROM benchmarks GROUP BY Brand,ModelName 
) MaxScores 
INNER JOIN 
(
    SELECT COUNT(1) ScoreCount,Brand,ModelName 
    FROM benchmarks GROUP BY Brand,ModelName 
) ScoreCounts 
USING (Brand,ModelName) 
GROUP BY Brand,ModelName 
) A GROUP BY MX) AA ORDER BY SC DESC,MX; 

此查詢完全產生你在找什麼，並將結果顯示在你的問題有它的確切順序。我用這個問題的樣本數據進行了試驗。這裏是我得到的：

mysql> use test 
Database changed 
mysql> drop table if exists benchmarks; 
Query OK, 0 rows affected (0.05 sec) 

mysql> CREATE TABLE benchmarks (Brand CHAR(2),ModelName CHAR(2),BenchMark INT,key (Brand,ModelName)); 
Query OK, 0 rows affected (0.14 sec) 

mysql> INSERT INTO benchmarks VALUES 
    -> ('B1','M1',1000), 
    -> ('B1','M1',2000), 
    -> ('B1','M2',3000), 
    -> ('B1','M2',2000), 
    -> ('B2','M1',3000), 
    -> ('B2','M3',4000); 
Query OK, 6 rows affected (0.03 sec) 
Records: 6 Duplicates: 0 Warnings: 0 

mysql> SHOW CREATE TABLE benchmarks\G 
*************************** 1. row *************************** 
     Table: benchmarks 
Create Table: CREATE TABLE `benchmarks` (
    `Brand` char(2) DEFAULT NULL, 
    `ModelName` char(2) DEFAULT NULL, 
    `BenchMark` int(11) DEFAULT NULL, 
    KEY `Brand` (`Brand`,`ModelName`) 
) ENGINE=InnoDB DEFAULT CHARSET=latin1 
1 row in set (0.00 sec) 

mysql> SELECT * FROM benchmarks; 
+-------+-----------+-----------+ 
| Brand | ModelName | BenchMark | 
+-------+-----------+-----------+ 
| B1 | M1  |  1000 | 
| B1 | M1  |  2000 | 
| B1 | M2  |  3000 | 
| B1 | M2  |  2000 | 
| B2 | M1  |  3000 | 
| B2 | M3  |  4000 | 
+-------+-----------+-----------+ 
6 rows in set (0.01 sec) 

mysql> SELECT * FROM 
    -> (SELECT MX,COUNT(1) SC FROM 
    -> (SELECT MAX(MaxScores.MaxScore) MX,ScoreCounts.ScoreCount FROM 
    -> (
    ->  SELECT MAX(BenchMark) MaxScore,Brand,ModelName 
    ->  FROM benchmarks GROUP BY Brand,ModelName 
    ->) MaxScores 
    -> INNER JOIN 
    -> (
    ->  SELECT COUNT(1) ScoreCount,Brand,ModelName 
    ->  FROM benchmarks GROUP BY Brand,ModelName 
    ->) ScoreCounts 
    -> USING (Brand,ModelName) 
    -> GROUP BY Brand,ModelName 
    ->) A GROUP BY MX) AA ORDER BY SC DESC,MX; 
+------+----+ 
| MX | SC | 
+------+----+ 
| 3000 | 2 | 
| 2000 | 1 | 
| 4000 | 1 | 
+------+----+ 
3 rows in set (0.01 sec) 

試試看！

Answer 2

SELECT b.model, b.brand, bd.score, COUNT(*) 
FROM (
     SELECT model, brand, MAX(score) AS mscore 
     FROM benchmark 
     GROUP BY 
       model, brand 
     ) bd 
JOIN benchmark b 
ON  b.model = bd.model 
     AND b.brand = bd.brand 
     AND b.score = bd.mscore 
GROUP BY 
     b.model, b.brand 

上(model, brand, score)這個工作快速創建索引。

更新：

SELECT score, COUNT(*) AS cnt 
FROM benchmark 
GROUP BY 
     score 
ORDER BY 
     cnt DESC