多個MAX（）在同一個查詢

我： -

SELECT MAX(register_number) AS "Next-6-months-register-number" 
    FROM gypsum WHERE test_frequency ='6'

我想在同一個query.Is這可能test_frequency ='3'和'12'返回值是多少？謝謝GWS。

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2012-10-15 user1731603

是的，這是可能的。使用GROUP BY以獲得最大的價值爲每個組：

SELECT test_frequency, MAX(register_number) AS "Max-register-number" 
FROM gypsum 
WHERE test_frequency IN ('3', '6', '12') 
GROUP BY test_frequency

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2012-10-15 12:57:56

謝謝你標記這個工作的對待 – user1731603

SELECT 
    MAX(CASE WHEN test_frequency = '3' THEN register_number END) 
     AS "Next-3-months-register-number", 
    MAX(CASE WHEN test_frequency = '12' THEN register_number END) 
     AS "Next-12-months-register-number", 
    MAX(CASE WHEN test_frequency = '6' THEN register_number END) 
     AS "Next-6-months-register-number", 
    MAX(register_number) AS "Next-6-months-register-number" 
FROM gypsum

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2012-10-15 12:58:22

謝謝Mamoud這個工作，但返回4列與12重複 – user1731603

@ user1731603刪除'test_frequency'和'GROUP BY test_frequency'。看到我的編輯 –

感謝馬哈茂德，做到了。 – user1731603

試試這個

SELECT MAX(CASE 
       WHEN test_frequency ='6' THEN register_number 
      ELSE NULL END) AS "Next-6-months-register-number" , 
     MAX(CASE 
       WHEN test_frequency ='3' THEN register_number 
      ELSE NULL END) AS "Next-3-months-register-number" , 
    MAX(CASE 
       WHEN test_frequency ='12' THEN register_number 
      ELSE NULL END) AS "Next-12-months-register-number" 
FROM gypsum

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2012-10-15 12:58:30

謝謝rs我無法得到這個工作有一個錯誤：錯誤代碼：1064 你有你的SQL語法錯誤;檢查對應於您的MySQL服務器版本的手冊，以便在'）AS「Next-6-months-register-number」附近使用正確的語法， MAX（CASE WHEN te'at line 3 – user1731603

Thanks但我仍然得到錯誤代碼：1064 您的SQL語法錯誤;請查看與您的MySQL服務器版本相對應的手冊，以查看'MAX（CASE WHEN test_frequency ='3'THEN register_number 'at第4行 – user1731603

現在檢查，查詢時在列之間缺少一個逗號 –

爲了獲得最大價值的所有test_frequency

SELECT test_frequency ,MAX(register_number) AS "Next-6-months-register-number" 
FROM gypsum 
group by test_frequency

SELECT MAX(register_number) AS "Next-6-months-register-number" 
FROM gypsum WHERE test_frequency in('6','3','12') 
group by test_frequency

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2012-10-15 12:58:59 AnandPhadke

感謝您的回答阿南德 – user1731603

您應該可以只添加或關鍵字的額外參數。

SELECT MAX(register_number) AS "Next-6-months-register-number" FROM gypsum 
WHERE test_frequency ='6' 
or 
test_frequency ='3' 
or 
test_frequency ='12'

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2012-10-15 12:59:13

感謝您的回答Stephen – user1731603

在這裏，你從查詢添加您的測試頻率。（ '3'，'12）..或選擇，如：

SELECT test_frequency, MAX(register_number) AS "Max-register-number" 
FROM gypsum 
WHERE test_frequency IN ('3','12') 
GROUP BY test_frequency

SELECT test_frequency, MAX(register_number) AS "Max-register-number" 
FROM gypsum 
WHERE test_frequency IN (select frequency_colname from tablename where colname=value) 
GROUP BY test_frequency

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2012-10-15 13:07:16 jainvikram444

多個MAX（）在同一個查詢

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