编写mysql查询的想法_Mysql_Sql_Wordpress

编写mysql查询的想法

mysql sql wordpress

编写mysql查询的想法,mysql,sql,wordpress,Mysql,Sql,Wordpress,我有一个名为wp\u bp\u activity的表，其中有许多列，我认为我应该使用其中的4个来解决这个问题：id，type，item\u id和date\u recorded 1-当有人发布新活动时，类型为activity\u update，item\u id为0 2-当有人在活动上发布新评论时，其类型为activity\u comment，item\u id为id列中存在的活动id 3-在这两种情况下，date\u recorded是插入数据的日期表中还有更多的types 但我只想获取最近

我有一个名为

wp\u bp\u activity

的表，其中有许多列，我认为我应该使用其中的4个来解决这个问题：

id

，

type

，

item\u id

和

date\u recorded

1-当有人发布新活动时，

类型为activity\u update
，item\u id
为0

2-当有人在活动上发布新评论时，其类型为activity\u comment
，item\u id
为id列中存在的活动id
3-在这两种情况下，date\u recorded
是插入数据的日期
表中还有更多的type
s
但我只想获取最近有人回复的类型为活动更新的行或是新的行（我认为基于记录的日期）
我试过的是：
SELECT  a.*, b.*
FROM wp_bp_activity as a, wp_bp_activity as b
WHERE
  ((b.type = 'activity_update') OR (b.type = 'activity_comment' AND b.item_id = a.id))
order by cast(a.date_recorded as datetime) desc
limit 0,20

执行时间太长，并以内存不足错误结束
感谢您对此类查询的任何帮助
更新#1
我希望此表中的哪些行是按此顺序排列的ID:
12079
12080

我不想得到的：
12079
12080

活动\u注释
类型
行的提取顺序是什么？
如您所见，带有activity\u comment
类型的行有一个item\u id
，其值为12079
。因此，12079
是最近有人对此发表评论的最新活动，12080
没有评论，只是刚刚发布。所以我两个都要，但顺序如下：
12079
12080

在OR子句中有联接条件。这是一个很好的例子，说明了为什么不应该使用这种语法
SELECT  a.*, b.*
FROM wp_bp_activity as a JOIN wp_bp_activity as b ON b.item_id = a.id
WHERE
  ((b.type = 'activity_update') OR (b.type = 'activity_comment'))
order by cast(a.date_recorded as datetime) desc
limit 0,20

在OR子句中有联接条件。这是一个很好的例子，说明了为什么不应该使用这种语法
SELECT  a.*, b.*
FROM wp_bp_activity as a JOIN wp_bp_activity as b ON b.item_id = a.id
WHERE
  ((b.type = 'activity_update') OR (b.type = 'activity_comment'))
order by cast(a.date_recorded as datetime) desc
limit 0,20

在OR子句中有联接条件。这是一个很好的例子，说明了为什么不应该使用这种语法
SELECT  a.*, b.*
FROM wp_bp_activity as a JOIN wp_bp_activity as b ON b.item_id = a.id
WHERE
  ((b.type = 'activity_update') OR (b.type = 'activity_comment'))
order by cast(a.date_recorded as datetime) desc
limit 0,20

在OR子句中有联接条件。这是一个很好的例子，说明了为什么不应该使用这种语法
SELECT  a.*, b.*
FROM wp_bp_activity as a JOIN wp_bp_activity as b ON b.item_id = a.id
WHERE
  ((b.type = 'activity_update') OR (b.type = 'activity_comment'))
order by cast(a.date_recorded as datetime) desc
limit 0,20

您应该再添加一个字段
id, type, item_id, commented_on, date_recorded

：：->>评论
将证明项目id
评论
，这里是12080的12079条评论，因此您可能很容易得到想要的东西
因此，您的结构应该如下所示：
   id             type            commented_on   item_id         date_recorded
|---------|-----------------------|-----------|-----------|--------------------------
|  12081  |   activity_comment    |   12080   |   12079   |    2013-10-18 07:27:01
|---------|-----------------------|-----------|-----------|--------------------------
|  12080  |   activity_update     |     0     |     0     |    2013-10-18 07:26:40
|---------|-----------------------|-----------|-----------|--------------------------
|  12079  |   activity_update     |     0     |     0     |    2013-10-17 05:15:43

您应该再添加一个字段
id, type, item_id, commented_on, date_recorded

：：->>评论
将证明项目id
评论
，这里是12080的12079条评论，因此您可能很容易得到想要的东西
因此，您的结构应该如下所示：
   id             type            commented_on   item_id         date_recorded
|---------|-----------------------|-----------|-----------|--------------------------
|  12081  |   activity_comment    |   12080   |   12079   |    2013-10-18 07:27:01
|---------|-----------------------|-----------|-----------|--------------------------
|  12080  |   activity_update     |     0     |     0     |    2013-10-18 07:26:40
|---------|-----------------------|-----------|-----------|--------------------------
|  12079  |   activity_update     |     0     |     0     |    2013-10-17 05:15:43

您应该再添加一个字段
id, type, item_id, commented_on, date_recorded

：：->>评论
将证明项目id
评论
，这里是12080的12079条评论，因此您可能很容易得到想要的东西
因此，您的结构应该如下所示：
   id             type            commented_on   item_id         date_recorded
|---------|-----------------------|-----------|-----------|--------------------------
|  12081  |   activity_comment    |   12080   |   12079   |    2013-10-18 07:27:01
|---------|-----------------------|-----------|-----------|--------------------------
|  12080  |   activity_update     |     0     |     0     |    2013-10-18 07:26:40
|---------|-----------------------|-----------|-----------|--------------------------
|  12079  |   activity_update     |     0     |     0     |    2013-10-17 05:15:43

您应该再添加一个字段
id, type, item_id, commented_on, date_recorded

：：->>评论
将证明项目id
评论
，这里是12080的12079条评论，因此您可能很容易得到想要的东西
因此，您的结构应该如下所示：
   id             type            commented_on   item_id         date_recorded
|---------|-----------------------|-----------|-----------|--------------------------
|  12081  |   activity_comment    |   12080   |   12079   |    2013-10-18 07:27:01
|---------|-----------------------|-----------|-----------|--------------------------
|  12080  |   activity_update     |     0     |     0     |    2013-10-18 07:26:40
|---------|-----------------------|-----------|-----------|--------------------------
|  12079  |   activity_update     |     0     |     0     |    2013-10-17 05:15:43

也许我错过了一些重要的东西，但这有什么不对
SELECT *
FROM `wp_bp_activity`
WHERE `type`='activity_update'
ORDER BY `date_recorded` ASC
LIMIT 0, 20;

也许我错过了一些重要的东西，但这有什么不对
SELECT *
FROM `wp_bp_activity`
WHERE `type`='activity_update'
ORDER BY `date_recorded` ASC
LIMIT 0, 20;

也许我错过了一些重要的东西，但这有什么不对
SELECT *
FROM `wp_bp_activity`
WHERE `type`='activity_update'
ORDER BY `date_recorded` ASC
LIMIT 0, 20;

也许我错过了一些重要的东西，但这有什么不对
SELECT *
FROM `wp_bp_activity`
WHERE `type`='activity_update'
ORDER BY `date_recorded` ASC
LIMIT 0, 20;

我假设您正在查找“最近的条目”（WHERE type='activity\u update'和date\u recorded>[threshold]
）和“具有最近回复的条目，无论条目的年龄如何”（WHERE reply.type='activity\u comment'和reply.date\u recorded>[threshold]
）
第一组很简单：
SELECT entries.*
FROM activity AS entries
WHERE type = 'activity_update' AND date_recorded > [threshold]

第二组不太明显：
SELECT entries.*
FROM activity AS entries
JOIN activity AS replies
    ON replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND replies.date_recorded > [threshold]

总而言之：
SELECT entries.*
FROM activity AS entries
LEFT JOIN activity AS replies -- LEFT JOIN, because an INNER JOIN would filter out entries without any reply
    ON  replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND (
        entries.date_recorded > [threshold]
        OR replies.date_recorded > [threshold] -- evaluates as FALSE if replies.date_recorded is NULL
    )
ORDER BY IFNULL(replies.date_recorded, entries.date_recorded) -- replies if not null, entries otherwise

我并不为我的“按顺序排列”条款表现不佳而感到自豪，我希望有人能提出更好的建议
我假设您正在寻找“最近的条目”（其中type='activity\u update'和date\u recorded>[threshold]
）和“具有最近回复的条目，无论条目的年龄如何”（其中reply.type='activity\u comment'和reply.date\u recorded>[阈值]
）
第一组很简单：
SELECT entries.*
FROM activity AS entries
WHERE type = 'activity_update' AND date_recorded > [threshold]

第二组不太明显：
SELECT entries.*
FROM activity AS entries
JOIN activity AS replies
    ON replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND replies.date_recorded > [threshold]

总而言之：
SELECT entries.*
FROM activity AS entries
LEFT JOIN activity AS replies -- LEFT JOIN, because an INNER JOIN would filter out entries without any reply
    ON  replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND (
        entries.date_recorded > [threshold]
        OR replies.date_recorded > [threshold] -- evaluates as FALSE if replies.date_recorded is NULL
    )
ORDER BY IFNULL(replies.date_recorded, entries.date_recorded) -- replies if not null, entries otherwise

我并不为我的“按顺序排列”条款表现不佳而感到自豪，我希望有人能提出更好的建议
我假设您正在寻找“最近的条目”（其中type='activity\u update'和date\u recorded>[threshold]
）和“具有最近回复的条目，无论条目的年龄如何”（其中reply.type='activity\u comment'和reply.date\u recorded>[阈值]
）
第一组很简单：
SELECT entries.*
FROM activity AS entries
WHERE type = 'activity_update' AND date_recorded > [threshold]

第二组不太明显：
SELECT entries.*
FROM activity AS entries
JOIN activity AS replies
    ON replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND replies.date_recorded > [threshold]

总而言之：
SELECT entries.*
FROM activity AS entries
LEFT JOIN activity AS replies -- LEFT JOIN, because an INNER JOIN would filter out entries without any reply
    ON  replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND (
        entries.date_recorded > [threshold]
        OR replies.date_recorded > [threshold] -- evaluates as FALSE if replies.date_recorded is NULL
    )
ORDER BY IFNULL(replies.date_recorded, entries.date_recorded) -- replies if not null, entries otherwise

我并不为我的“按顺序排列”条款表现不佳而感到自豪，我希望有人能提出更好的建议
我假设您正在寻找“最近的条目”（其中type='activity\u update'和date\u recorded>[threshold]
）和“具有最近回复的条目，无论条目的年龄如何”（其中reply.type='activity\u comment'和reply.date\u recorded>[阈值]
）
第一组很简单：
SELECT entries.*
FROM activity AS entries
WHERE type = 'activity_update' AND date_recorded > [threshold]

第二组不太明显：
SELECT entries.*
FROM activity AS entries
JOIN activity AS replies
    ON replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND replies.date_recorded > [threshold]

总而言之：
SELECT entries.*
FROM activity AS entries
LEFT JOIN activity AS replies -- LEFT JOIN, because an INNER JOIN would filter out entries without any reply
    ON  replies.item_id = entries.id
    AND replies.type = 'activity_comment'
WHERE
    entries.type = 'activity_update'
    AND (
        entries.date_recorded > [threshold]
        OR replies.date_recorded > [threshold] -- evaluates as FALSE if replies.date_recorded is NULL
    )
ORDER BY IFNULL(replies.date_recorded, entries.date_recorded) -- replies if not null, entries otherwise

我并不为我糟糕的orderby
子句感到自豪，我希望有人能建议一个更好的主意
在你的查询中，所有的结果都必须有b.item=a.id
但是在我的查询中，b.item=a.id
应该只在b.type='activity\u comment'时才相等。
我需要根据最近的活动来排序结果获得评论