Php 将同一个表上的多个MySQL查询合并为一个查询

如何在同一个表上进行多个查询，选择不同的列

如果有帮助的话。。。所有查询在SQL语句的select部分都有一个公共列。它们都选择

ID

，然后再选择特定的内容

因此，每个查询都需要

ID

和以下任一项：

post\u name

，

post\u title

，或

post\u摘录

如果它有助于简化事情。我试图在这些列中搜索广泛匹配和精确匹配

因此，在我的示例中，我将在以下列中查找：“地板饰面”、“地板”或“饰面”：

post\u name

、

post\u title

、以及

post\u摘录

。都在同一张桌子里

我试图通过

联合

来实现这一点

以下是我的疑问：

Array
(
    [broad] => Array
        (
            [floor] => Array
                (
                    [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%'
                    [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%'
                    [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%'
                )

            [finish] => Array
                (
                    [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%'
                    [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%'
                    [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%'
                )

        )

    [exact] => Array
        (
            [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%'
            [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%'
            [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%'
        )

    [combined] => ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%' ) UNION ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%' )
)

Array
        (
            [broad] => Array
                (
                    [floor] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor' )
                    [finish] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%' )
                )

            [exact] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%' )
            [combined] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%' ) UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor%' )) UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%' ))
        )

)

然而，上述结果很有趣。我似乎得到了所有正确的结果，但每个结果值的键（应该是列的名称）始终保持不变。它总是

post\u name

，即使分配给它的值可能是

post\u title

或

post\u摘录

因此每个结果都有一个

ID

和

post\u name

。基本上，它们的键是错误的，但值似乎是准确的

我也尝试过类似的方法：

Array
(
    [broad] => Array
        (
            [floor] => Array
                (
                    [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%'
                    [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%'
                    [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%'
                )

            [finish] => Array
                (
                    [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%'
                    [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%'
                    [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%'
                )

        )

    [exact] => Array
        (
            [slugs] => SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%'
            [titles] => SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%'
            [excerpts] => SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%'
        )

    [combined] => ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor-finish%' ) UNION ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_name` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_name` LIKE '%finish%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor finish%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_title` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_title` LIKE '%finish%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor finish%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%floor%' ) UNION ( SELECT `ID`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND `post_excerpt` LIKE '%finish%' )
)

Array
        (
            [broad] => Array
                (
                    [floor] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor' )
                    [finish] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%' )
                )

            [exact] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%' )
            [combined] => SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor-finish%' OR `post_title` LIKE '%floor finish%' OR `post_excerpt` LIKE '%floor finish%' ) UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%floor%' OR `post_title` LIKE '%floor%' OR `post_excerpt` LIKE '%floor%' )) UNION (SELECT `ID`, `post_name`, `post_title`, `post_excerpt` FROM tps_3_posts WHERE `post_status` = 'publish' AND ( `post_name` LIKE '%finish%' OR `post_title` LIKE '%finish%' OR `post_excerpt` LIKE '%finish%' ))
        )

)

这更符合我想要实现的目标。我希望每个结果都有

ID

，

post\u摘录

，

post\u slug

，以及

post\u标题

。如果没有匹配项，则使用空值显示它们的键，或者完全不显示键

第二次尝试的问题是，它只需要在三个所需列中的一个中进行匹配。因此，如果它在

post\u摘录

中匹配，并且没有其他地方匹配，它仍然会从

post\u标题

和

post\u名称

中提取值。从而使结果不准确

我读过几个看似相似的问题，但大多数都没有真正明确的答案。。。或这些问题/答案更适合单独表格上的多个查询

关于在同一个表上组合多个MySQL查询有什么指导或建议吗？

顺便说一下。。。我在两个示例中都使用“组合”作为发送到数据库的最终查询

---

所以，再来一次。。。如果列中没有匹配项，则将它们的键显示为null，或者完全忽略结果中的键。

正如我在第二种情况中所理解的，问题是只有匹配的列应该有值，其他列应该为null。对于这种情况，您可以在SELECT中使用IF/ELSE或WHEN语句。其思想是选择“实际值”是指该列的值对应于预期值，否则为空

另一个可能的解决方案是你可以写

SELECT `ID`, `post_name`, `post_title`, 'post_excerpt'

所以，您可以选择WHERE语句中作为条件的字符串值，以后可以使用该值来了解此行所属的内容

由于查询中的

UNION

语句，您得到了错误的“key”。您有不同的键名，但在联合查询的三个不同列之间有兼容的列类型。数据库引擎不是抛出错误，而是从第一个查询中选取列名，并将其用于所有查询：

id | post_name # <= column name in first query
1  | "my post"

UNION

id | post_title # <= column name is different, but type is compatible, so UNION succeeds
1  | "my post title"

UNION

id | post_excerpt # <= ditto
1  | "my post excerpt"

在您的表格中，此功能的基本版本可能如下所示：

SELECT ID, post_name, null AS post_title, null AS post_excerpt FROM tps_3_posts

UNION

SELECT ID, null AS post_name, post_title, null AS post_excerpt FROM tps_3_posts

UNION

SELECT ID, null AS post_name, null AS post_title, post_excerpt FROM tps_3_posts

---

这可能对您正在尝试的操作更有用。如果你想看到它付诸实施。

我想我理解你的建议。我应该在每个查询中选择所有4列，但强制某些列为空？这似乎是一个愚蠢的问题，但如何故意为某些列选择空值，而不为其他列选择空值？@MichaelEcklund请参阅我的更新答案，了解一个基本查询示例。非常感谢。这正是我需要做的。顺便说一句，W3学校教我做

选择列名作为别名

，你演示

选择别名作为列名

。您的语法是正确的，但语法是不正确的。当我这样做时，MySQL会抛出一个无效语法错误。按照你的方式，它工作得很完美。

SELECT ID, post_name, null AS post_title, null AS post_excerpt FROM tps_3_posts

UNION

SELECT ID, null AS post_name, post_title, null AS post_excerpt FROM tps_3_posts

UNION

SELECT ID, null AS post_name, null AS post_title, post_excerpt FROM tps_3_posts