如何从一个表中连接多个字段并将结果与​​另一个表中的另一个字段进行比较？

Question

我有以下情况：

table 1 -> publications

table 2 -> users

在出版物的一些细节的表一中，我有20个关于作者的字段，它们的名称和姓氏（这些字段：n1, l1, n2, l2, n3, l3...等等）。

在表2中，我有一个字段，其中包含用户的名称和姓氏。

我想只显示这些出版物，其中表1中的名称和姓氏与表2中的名称和姓氏相同。

到目前为止，这是我的查询：

$sql ="SELECT *, concat_ws(' ',n1,l1), concat_ws(' ',n2,l2) AS my
       FROM #__publications WHERE my IN
       (SELECT name FROM #__users WHERE name = '".$l_user."')";

我知道可能我的思维方式错了。你可以帮帮我吗？如果你能给我一些建议，我将不胜感激。

Answer 1

您应该从Publications表中删除作者，并创建一个将用户与出版物链接起来的第3个表。

PublicationAuthors

PublicationID  int
UserID int

然后您的查询可以检查该表以查看用户是否与该发布相关联。此外，您可以根据需要拥有尽可能多的作者，而无需向出版物添加新列，如果有人更改其名称，则不会破坏与出版物的关系。

以下是一个示例（我使用SQL Server，因此可能存在较小的语法差异）：

CREATE TABLE Publications(
    [PublicationID] [int] IDENTITY(1,1) NOT NULL,
    [Title] [nvarchar](128) NOT NULL,
    [DatePublished] [DateTime]
PRIMARY KEY CLUSTERED 
(
    [PublicationID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO

CREATE TABLE Authors(
    [AuthorID] [int] IDENTITY(1,1) NOT NULL,
    [FirstName] [nvarchar](128) NOT NULL,
    [LastName] [nvarchar](128) NOT NULL
PRIMARY KEY CLUSTERED 
(
    [AuthorID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO


CREATE TABLE PublicationAuthors(
    [PublicationID] [int],
    [AuthorID] [int]
PRIMARY KEY CLUSTERED
(
    [PublicationID] ASC,
    [AuthorID]
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]
GO


INSERT INTO Publications (Title, DatePublished) VALUES ('Sphere', '5/12/1987')
INSERT INTO Publications (Title, DatePublished) VALUES ('Jurassic Park', '11/1/1990') 
INSERT INTO Authors (FirstName, LastName) VALUES ('Michael', 'Chricton')
INSERT INTO Authors (FirstName, LastName) VALUES ('Andy', 'McKenna')
INSERT INTO PublicationAuthors (PublicationID, AuthorID) VALUES (1, 1)
INSERT INTO PublicationAuthors (PublicationID, AuthorID) VALUES (2, 1)
INSERT INTO PublicationAuthors (PublicationID, AuthorID) VALUES (2, 2)

--All Authors for this Publication
SELECT p.Title, p.DatePublished, a.FirstName, a.LastName
FROM Publications p
INNER JOIN PublicationAuthors pa
   ON pa.PublicationID = p.PublicationID
INNER JOIN Authors a
   ON a.AuthorID = pa.AuthorID
WHERE p.PublicationID = 2

--All Publications for this Author
SELECT p.Title, p.DatePublished, a.FirstName, a.LastName
FROM Authors a
INNER JOIN PublicationAuthors pa
   ON pa.AuthorID = a.AuthorID
INNER JOIN Publications p
   ON pa.PublicationID = p.PublicationID
WHERE a.AuthorID = 1

然后当你意识到我拼错了作者的姓氏时，你可以在不触及出版物表的情况下更新那一行。

Answer 2

您可能会发现更容易设置用户表以包含user_id字段作为主键，并将其用作发布表中的索引。

CREATE TABLE __users
(
    user_id int(11) unsigned not null auto_increment,
    name varchar(32) not null default '',
    .... snip ....
    PRIMARY KEY (user_id)
);

CREATE TABLE __publications
(
    publication_id int(11) unsigned not null auto_increment, 
    user_id1 int(11) unsigned not null default 0,
    user_id2 int(11) unsigned not null default 0,
    n1 varchar(32) not null default '',
    l1 varchar(32) not null default '',
    n2 varchar(32) not null default '',
    l2 varchar(32) not null default '',
    .... snip ....
    PRIMARY KEY (publication_id),
    INDEX user_id1 (user_id1),
    INDEX user_id2 (user_id2)
);

SELECT p.*,  concat_ws(' ', p.n1, p.l1) AS author1,  concat_ws(' ', p.n2, p.l2) AS author2
FROM __users AS u
JOIN __publications AS p ON (u.user_id = p.user_id1 OR u.user_id = p.user_id2)
WHERE u.name = $1_user
GROUP BY p.publication_id

或者你可以像这样执行连接：

SELECT p.*,  concat_ws(' ', p.n1, p.l1) AS author1,  concat_ws(' ', p.n2, p.l2) AS author2
FROM __users AS u
JOIN __publications AS p ON (u.name = concat_ws(' ', p.n1, p.l1) OR u.name = concat_ws(' ', p.n2, p.l2))
WHERE u.name = $1_user
GROUP BY p.publication_id