mysql - 在 MySQL 中将三个表的多行合并为一行

Question

我读了问题Combine multiple rows into one row MySQL该示例展示了如何从 SELECT 语句的多行中生成单行结果。 SQL Fiddle with Demo也运行良好。在该问题中，有两个表:t1 和 t2。我的问题有三个表，我已经针对这个问题简化了它们:

表语言:

ID              INT(11)         NOT NULL    PRIMARY_KEY
name            VARCHAR(255)    NOT NULL    UNIQUE

表languages_have_persons:

Languages_ID    INT(11)         NOT NULL    PRIMARY_KEY
Persons_ID  INT(11)             NOT NULL    

表格人员:

ID              INT(11)         NOT NULL    PRIMARY_KEY
firstName       VARCHAR(255)    NOT NULL
lastName        VARCHAR(255)    NOT NULL

我想做的是类似地组合这些表，但我现在几个小时都没有这样做。这是我最后一次尝试:

SELECT p1.ID
    , p1.firstName
    , p1.lastName
    CONCAT_WS(', '
        , l2de.name
        , l2en.name
    )
    FROM
        languages_have_persons AS lp, persons AS p1
    LEFT JOIN languages AS l2de ON
        l2de.ID = 4 -- German
    LEFT JOIN languages AS l2en ON
        l2en.ID = 5 -- English
WHERE p1.ID = lp.Persons_ID
ORDER BY lastName, firstName;

错误消息如下:

Fehler
SQL-Befehl: Dokumentation


SELECT p1.ID AS ID
    , p1.firstName AS firstName
    , p1.lastName AS lastName
    CONCAT_WS(', '
        , l2de.name
        , l2en.name
    )
    FROM
        languages_have_persons AS lp, persons AS p1
    LEFT JOIN languages AS l2de ON
        l2de.ID = 4     LEFT JOIN languages AS l2en ON
        l2en.ID = 5 WHERE p1.ID = lp.Persons_ID
ORDER BY lastName, firstName LIMIT 0, 25
MySQL meldet: Dokumentation

#1064 - Fehler in der SQL-Syntax. Bitte die korrekte Syntax im Handbuch
nachschlagen bei '(', '
        , l2de.name
        , l2en.name
    )
    FROM
        languages_have_persons AS lp, ' in Zeile 4

我还尝试了其他方法，但没有一个语法正确。我想要的结果如下:

表语言:

ID    name
4     German
5     English

表language_have_persons:

Languages_ID    Persons_ID    
    4                2
    5                1
    5                2

表格人员:

ID    firstName    lastName
1     Joe           Frazier
2     Arnold        Schwarzenegger

我对正确的 SELECT 语句的期望是这样的

firstName    lastName           CONCAT_WS(…
Joe           Frazier           English
Arnold        Schwarzenegger    German, English

您看到上面 SQL 语法中的错误了吗？如果没有，你知道如何解决吗？

感谢您的帮助!

Answer 1

SELECT p1.ID
    , p1.firstName
    , p1.lastName,<--------------------I had made change at this line
    CONCAT_WS(', '
        , l2de.name
        , l2en.name
    )
    FROM
        languages_have_persons AS lp, persons AS p1
    LEFT JOIN languages AS l2de ON
        l2de.ID = 4 -- German
    LEFT JOIN languages AS l2en ON
        l2en.ID = 5 -- English
WHERE p1.ID = lp.Persons_ID
ORDER BY lastName, firstName;

或者，为了进一步查询，您可以尝试以下操作。

SELECT p1.ID
    , p1.firstName
    , p1.lastName,
    l2de.name
    FROM
    persons p1
    INNER JOIN languages_have_persons lp on p1.ID=lp.Persons_ID 
    INNER JOIN language l2de on l2de.ID=lp.Languages_ID 
    WHERE l2de.ID  IN(4,5)
    ORDER BY lastName, firstName;

您可以尝试上面的查询。