的Oracle SQL SELECT查詢

我有這個表：的Oracle SQL SELECT查詢

select * from scott.test; 

a b c 
--------- 
26 R 4 
26 T 5 
26 S 2 
25 Y 2 
25 U 3 
24 X 3 
22 Z 3 
21 P 3

我需要的是這樣的：對於給定的「一」我要提取所有的細節（A，B，C），如果有多一個「a」，我想只提取最高的「c」。例如，對於26，我想只提取：

a b c 
26 T 5

我已經以這種方式做到了這一點：

select * from scott.test where a = 26 and c = (select max(c) from scott.test where a = 26);

，但我需要它只有一個選擇（內選擇不選擇）。它可以完成嗎？謝謝！

來源

2015-10-20 user3913719

您需要使用** CASE **和** ROW_NUMBER **分析函數。在你的問題中，你的意思是** asap **？爲了儘快得到答案，你應該提供一個工作測試用例。創建並插入語句。至少SQL小提琴。顯示數據對誰想幫助你沒有幫助。你在一張桌子上執行一個SQL，所以只看數據的人只能* GUESS *而不能給你完全正確的答案。 –

@LalitKumarB我認爲他希望答案儘快（儘快） - *我認爲這是非常粗魯* –

@RaduGheorghiu我知道。我正在向OP解釋。 –

是否這樣？ -

WITH test 
    AS (SELECT 26 AS a, 'R' AS b, 4 AS c FROM dual 
     UNION ALL 
     SELECT 26 AS a, 'T' AS b, 5 AS c FROM dual 
     UNION ALL 
     SELECT 26 AS a, 'S' AS b, 2 AS c FROM dual 
     UNION ALL 
     SELECT 25 AS a, 'Y' AS b, 2 AS c FROM dual 
     UNION ALL 
     SELECT 25 AS a, 'U' AS b, 3 AS c FROM dual 
     UNION ALL 
     SELECT 24 AS a, 'X' AS b, 3 AS c FROM dual 
     UNION ALL 
     SELECT 22 AS a, 'Z' AS b, 3 AS c FROM dual 
     UNION ALL 
     SELECT 21 AS a, 'P' AS b, 3 AS c FROM dual) 
SELECT a, b, c 
    FROM (SELECT a, b, c, max(c) OVER (PARTITION BY a) AS max_c 
      FROM test 
     WHERE A = 26) 
WHERE c = max_c

來源

2015-10-20 15:07:36 Stawros

它看起來不像..一個選擇，但兩個，即使它們嵌套。 –

如果@ user3913719講述了單個表掃描，那麼多少個子查詢就無關緊要。不知道「選擇內不選擇」是什麼意思:) – Stawros

是的，我同意你的看法，但是OP是否提到過任何有關表掃描的內容？ –

使用ROW_NUMBER（）解析功能，你可以實現它。但是，您需要使用子查詢來完成此操作。但你總是可以用WITH從句來看它的不同。

以下查詢會提示您輸入列a的值，然後返回列的最大值爲c的行。 WITH子句的第一部分僅用於構建用於演示的示例數據，您只需要第二部分，即t。

例如，

爲a爲26輸入值：

SQL> WITH data AS 
    2 (SELECT 26 AS a, 'R' AS b, 4 AS c FROM dual 
    3 UNION ALL 
    4 SELECT 26 AS a, 'T' AS b, 5 AS c FROM dual 
    5 UNION ALL 
    6 SELECT 26 AS a, 'S' AS b, 2 AS c FROM dual 
    7 UNION ALL 
    8 SELECT 25 AS a, 'Y' AS b, 2 AS c FROM dual 
    9 UNION ALL 
10 SELECT 25 AS a, 'U' AS b, 3 AS c FROM dual 
11 UNION ALL 
12 SELECT 24 AS a, 'X' AS b, 3 AS c FROM dual 
13 UNION ALL 
14 SELECT 22 AS a, 'Z' AS b, 3 AS c FROM dual 
15 UNION ALL 
16 SELECT 21 AS a, 'P' AS b, 3 AS c FROM dual 
17 ), 
18 t AS 
19 (SELECT a,b,c,row_number() OVER(PARTITION BY a ORDER BY c DESC) rn FROM DATA 
20 ) 
21 SELECT a,b,c FROM t WHERE a = &1 AND rn = 1; 
Enter value for 1: 26 
old 21: SELECT a,b,c FROM t WHERE a = &1 AND rn = 1 
new 21: SELECT a,b,c FROM t WHERE a = 26 AND rn = 1 

     A B   C 
---------- - ---------- 
     26 T   5

爲a爲25輸入值：

SQL> WITH data AS 
    2 (SELECT 26 AS a, 'R' AS b, 4 AS c FROM dual 
    3 UNION ALL 
    4 SELECT 26 AS a, 'T' AS b, 5 AS c FROM dual 
    5 UNION ALL 
    6 SELECT 26 AS a, 'S' AS b, 2 AS c FROM dual 
    7 UNION ALL 
    8 SELECT 25 AS a, 'Y' AS b, 2 AS c FROM dual 
    9 UNION ALL 
10 SELECT 25 AS a, 'U' AS b, 3 AS c FROM dual 
11 UNION ALL 
12 SELECT 24 AS a, 'X' AS b, 3 AS c FROM dual 
13 UNION ALL 
14 SELECT 22 AS a, 'Z' AS b, 3 AS c FROM dual 
15 UNION ALL 
16 SELECT 21 AS a, 'P' AS b, 3 AS c FROM dual 
17 ), 
18 t AS 
19 (SELECT a,b,c,row_number() OVER(PARTITION BY a ORDER BY c DESC) rn FROM DATA 
20 ) 
21 SELECT a,b,c FROM t WHERE a = &1 AND rn = 1; 
Enter value for 1: 25 
old 21: SELECT a,b,c FROM t WHERE a = &1 AND rn = 1 
new 21: SELECT a,b,c FROM t WHERE a = 25 AND rn = 1 

     A B   C 
---------- - ---------- 
     25 U   3

來源

2015-10-20 15:38:03

試試這個。它可能應該工作:)。

select a,max(b) keep (dense_rank first order by c desc) b , max(c) keep (dense_rank first order by c desc) c from test 
    where a = 26 
    group by a

來源

2015-10-20 20:40:33

的Oracle SQL SELECT查詢

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