Question

我需要帮助一个带有ann ann的查询，我必须为每个健身成员超过5年的用户找到练习“Bench Press”和“Squat”的1 rep max（Max（Carico））。

我试过了：

    SELECT U.Nome,U.Cognome, MAX(P1.Carico) AS MaxSquat,MAX(P2.Carico) AS MaxBench
FROM utente AS U, scheda AS S1, programma AS P1,scheda AS S2, programma AS P2
WHERE U.CF IN(SELECT U.CF
                FROM Utente U
             WHERE Data_Iscrizione < date_sub(curdate(), interval 5 year))
        AND U.CF=S1.ID_Utente AND S1.ID_Scheda=P1.ID_Scheda
        AND U.CF=S2.ID_Utente AND S2.ID_Scheda=P2.ID_Scheda 
        AND P1.nRipetizioni=1 AND P1.Esercizio="Bench Press"
        AND P2.nRipetizioni=1 AND P2.Esercizio="Squat"
GROUP BY U.Nome,U.Cognome

我将此作为输出：

Nome    |Cognome|MaxSquat |MaxBench|
Mario   |lalala |   100   |  200   |
Simon   |jujuju |   130   |  100   |

但它没有显示具有Null值的元组

我想获得这样的输出：

Nome    |Cognome|MaxSquat |MaxBench|
John    |blabla |   90    |  Null  |
Carl    |lasdll |   Null  |  150   |
Mario   |lalala |   100   |  200   |
Simon   |jujuju |   130   |  100   |

我该怎么做？谢谢

Answer 1

当您在其中分段中说明条件时，您将只获得这些条件为真的结果。具体来说，你得到了你的结果：P1.Esercizio =＆＃34; Bench Press＆＃34;和P2.Esercizio =＆＃34; Squat＆＃34; （和其他一些条件）。

你需要的是没有P1的结果或P1的结果.Esercizio =＆＃34; Bench Press＆＃34; （以及许多其他条件）

这就是左连接的位置：从指定的第一个表中获取所有行，只从第二个表中获取可以匹配的行。移动 ALL 适用于在join子句的 on 关键字后允许不存在的表的条件

您可以将左连接置于严重状态并编写此

SELECT U.Nome
     , U.Cognome
     , MAX(P1.Carico) AS MaxSquat
     , MAX(P2.Carico) AS MaxBench
FROM   utente AS U
     left join scheda AS S1 on U.CF=S1.ID_Utente 
     left join programma AS P1 on S1.ID_Scheda=P1.ID_Scheda 
          AND P1.nRipetizioni=1 AND P1.Esercizio="Bench Press"
     left join scheda AS S2 on U.CF=S2.ID_Utente 
     left join programma AS P2 on S2.ID_Scheda=P2.ID_Scheda 
          AND P2.nRipetizioni=1 AND P2.Esercizio="Squat"
WHERE U.CF IN(SELECT U.CF
            FROM Utente U
         WHERE Data_Iscrizione < date_sub(curdate(), interval 5 year))
GROUP BY U.Nome, U.Cognome

我没有测试这段代码。如果你无法让它运行，请随时在评论中提及这一点，我会再次接受它。

sql查询结果不正确

1 个答案: