MySQL显示值为IS NULL或等于X的行

userPosts.value can contain one of two values: 0 or 1.

userPosts.value可以包含两个值之一：0或1。

I am Left Joining userPosts to my Posts table.

我正在将userPosts加入我的帖子表。

I want to get all posts from my Posts table where userPosts.value = 0 as well as all posts that do not have any userPosts.value at all (thus, NULL).

我想从我的Posts表中获取userPosts.value = 0的所有帖子以及根本没有任何userPosts.value的所有帖子（因此，NULL）。

The following only get me posts where value = 0 but no NULL:

以下只给我发布值为0但没有NULL的帖子：

SELECT * FROM $wpdb->posts
LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
WHERE userPosts.value != 1
ORDER BY $wpdb->posts.post_date DESC

The following only gets me posts where value = NULL:

以下只获取值为NULL的帖子：

SELECT * FROM $wpdb->posts
LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
WHERE userPosts.value IS NULL
ORDER BY $wpdb->posts.post_date DESC

but this yields no results at all:

但这根本不会产生任何结果：

SELECT * FROM $wpdb->posts
LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
WHERE userPosts.value = 0
AND userPosts.value IS NULL
ORDER BY $wpdb->posts.post_date DESC

and this does get me posts with value = 0 as well as NULL but it repeats all my NULL posts three times!

这确实得到了我的帖子值为0以及NULL，但它重复我的所有空白帖子三次！

SELECT * FROM $wpdb->posts
LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
WHERE userPosts.value = 0
OR userPosts.value IS NULL
ORDER BY $wpdb->posts.post_date DESC

So what am I doing wrong?

那么我做错了什么？

3 个解决方案

#1

Try to use parenthasis on OR condition (userContests.value = 0 OR userContests.value IS NULL)

尝试在OR条件上使用parenthasis（userContests.value = 0或userContests.value IS NULL）

 SELECT * FROM $wpdb->posts
    LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
    WHERE (userContests.value = 0
    OR userContests.value IS NULL)
    ORDER BY $wpdb->posts.post_date DESC

#2

(x = 0) AND (x is NULL) - a single field cannot be two values at the same time. No surprise that you get no results at all, because you've specified a where condition that is impossible to satisfy.

（x = 0）AND（x为NULL） - 单个字段不能同时为两个值。毫无疑问，你根本没有得到任何结果，因为你已经指定了一个无法满足的条件。

As for the rest of the query. You use $wdpd->posts as your source table, but then use a table named userContests in the where clause. Does $wpdb->posts resolve to userContests? If so, why make the table name dynamic in one place and hard-coded it in another?

至于其余的查询。您使用$ wdpd-> posts作为源表，但随后在where子句中使用名为userContests的表。 $ wpdb->帖子是否解析为userContests？如果是这样，为什么要在一个地方使表名动态并在另一个地方硬编码呢？

#3

You partially answered your own question in the title: OR not AND, but try using DISTINCT:

您在标题中部分回答了您自己的问题：或者不是AND，但尝试使用DISTINCT：

SELECT DISTINCT * FROM $wpdb->posts -- Note "DISTINCT"
LEFT JOIN userPosts ON ($wpdb->posts.ID = userPosts.postID)
WHERE userContests.value = 0
OR userContests.value IS NULL -- Note "OR"
ORDER BY $wpdb->posts.post_date DESC

#1