Mic*_*uel 12 php mysql sql database
我有3个表,其中包含以下数据:
第一个表称为连接,connections.username1其中跟随的connections.username2是跟随者.
它有以下几行:
connections.username1 | connections.username2
mikha | guy
guy | maricela
maricela | guy
第二个表叫问题.它有questions.asker_username一个专门为提问者调用的列,另一个用于接收调用问题的专栏questions.target_username.当提问者被称为"sys.tem"并且目标被称为"every.one"时,它被认为是一个全局问题,并且可以由所有成员回答.
匿名用户可以询问并将他们的IP记录为asker_username.
它有以下几行:
questions.id | questions.asker_username | questions.target_username | questions.question
1 | mikha | guy | what's your name?
2 | mikha | maricela | What's your age?
3 | guy | mikha | what's your name?
4 | maricela | guy | favorite food?
5 | xx.xx.xxx.xx | mikha | favorite pet?
6 | xx.xx.xxx.xx | guy | first name?
7 | xx.xx.xxx.xx | maricela | first name?
8 | sys.tem | every.one | what's ur name?
9 | sys.tem | every.one | favorite movie?
10 | sys.tem | every.one | favorite game?
第3个表称为答案.答案表中的id与问题ID相同.此表有一个id,用户名和答案列.
answers.id | answers.username | answers.answer
1 | guy | my name is guy
2 | maricela | my name is maricela
3 | mikha | my name is mikha
4 | guy | pizza
8 | guy | guy is my name
8 | maricela | maricela is my name
9 | maricela | avatar
我想要一个查询,它结合了以下与"mikha"相关的条件和他所遵循的人:
1)questions.asker_username不是"mikha"
2) questions.target_username是"mikha"或他跟随的任何用户.
3)如果questions.target_username等于"every.one"并由"mikha"回答,请显示问题.
4)如果questions.target_username等于"every.one"并由"mikha"跟随的任何人回答,请显示问题及其答案.如果"mikha"跟随的用户没有回答,请不要显示问题.
5)如果questions.target_username等于"every.one"并且根本没有任何人回答,请显示一次问题.
6)如果questions.target_username等于"every.one"并且没有被"mikha"回答并且没有被他跟随的任何人回答,则只显示一次问题.
我使用以下查询:
SELECT questions.id,answers.id,questions.asker_username,questions.target_username,
answers.username,questions.question,answers.answer
FROM questions
LEFT JOIN answers ON (questions.id = answers.id)
LEFT JOIN connections ON connections.username1 = 'mikha'
AND (questions.target_username = connections.username2
OR questions.asker_username = connections.username2
OR connections.username2 = answers.username)
WHERE questions.asker_username <> 'mikha'
AND (questions.target_username = 'mikha'
OR questions.target_username = connections.username2
OR (questions.target_username = 'every.one'
AND (answers.username = 'mikha'
OR answers.username = connections.username2
OR answers.username IS NULL)
)
)
GROUP BY questions.id,answers.username
结果我期待:
questions.id | answers.id | questions.asker_username | questions.target_username | answers.username | questions.question | answers.answer
3 | 3 | guy | mikha | mikha | what's your name? | my name is mikha
4 | 4 | maricela | guy | guy | favorite food? | pizza
5 | 5 | xx.xx.xxx.xx | mikha | NULL | favorite pet? | NULL
6 | 6 | xx.xx.xxx.xx | guy | NULL | first name? | NULL
8 | 8 | sys.tem | every.one | NULL | what's ur name? | NULL
8 | 8 | sys.tem | every.one | guy | what's ur name? | guy is my name
9 | 9 | sys.tem | every.one | NULL | favorite movie? | NULL
10 | 10 | sys.tem | every.one | NULL | favorite game? | NULL
我实际得到的结果:
questions.id | answers.id | questions.asker_username | questions.target_username | answers.username | questions.question | answers.answer
3 | 3 | guy | mikha | mikha | what's your name? | my name is mikha
4 | 4 | maricela | guy | guy | favorite food? | pizza
5 | 5 | xx.xx.xxx.xx | mikha | NULL | favorite pet? | NULL
6 | 6 | xx.xx.xxx.xx | guy | NULL | first name? | NULL
8 | 8 | sys.tem | every.one | guy | what's ur name? | guy is my name
10 | 10 | sys.tem | every.one | NULL | favorite game? | NULL
我在http://sqlfiddle.com/#!2/29929e/1上建立了一个方案,向您展示我实际得到的结果
谢谢 :)
好的,让我们从最简单的一个开始(你的第一条规则):
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
GROUP BY q.id,a.username
现在让我们添加你的第二条规则 - 现在增加了更多复杂性......
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
AND q.target_username = 'mikha'
OR q.target_username IN (
SELECT username2
FROM connections
WHERE username1 = 'mikha'
)
GROUP BY q.id,a.username
现在第三条规则(每个人都回答mikha):
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
AND q.target_username = 'mikha'
OR q.target_username IN (
SELECT username2
FROM connections
WHERE username1 = 'mikha'
)
OR (q.target_username = 'every.one' AND a.username = 'mikha')
GROUP BY q.id,a.username
现在为第四条规则:
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
AND q.target_username = 'mikha'
OR q.target_username IN (
SELECT username2
FROM connections
WHERE username1 = 'mikha'
)
OR (q.target_username = 'every.one' AND a.username = 'mikha')
OR (q.target_username = 'every.one' AND a.username IN (
SELECT username2
FROM connections
INNER JOIN answers ON answers.username = connections.username2
AND answers.answers IS NOT NULL
WHERE username1 = 'mikha'
))
GROUP BY q.id,a.username
第五条规则(耶稣!):
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
AND q.target_username = 'mikha'
OR q.target_username IN (
SELECT username2
FROM connections
WHERE username1 = 'mikha'
)
OR (q.target_username = 'every.one' AND a.username = 'mikha')
OR (q.target_username = 'every.one' AND a.username IN (
SELECT username2
FROM connections
INNER JOIN answers ON answers.username = connections.username2
AND answers.answers IS NOT NULL
WHERE username1 = 'mikha'
))
OR (q.target_username = 'every.one' AND a.answer IS NULL)
GROUP BY q.id,a.username
对于最后一个:
SELECT q.id, a.id, q.asker_username, q.target_username, a.username, q.question, a.answer
FROM questions q
LEFT JOIN answers a ON q.id = a.id
WHERE q.asker_username <> 'mikha'
AND q.target_username = 'mikha'
OR q.target_username IN (
SELECT username2
FROM connections
WHERE username1 = 'mikha'
)
OR (q.target_username = 'every.one' AND a.username = 'mikha')
OR (q.target_username = 'every.one' AND a.username IN (
SELECT username2
FROM connections
INNER JOIN answers ON answers.username = connections.username2
AND answers.answers IS NOT NULL
WHERE username1 = 'mikha'
))
OR (q.target_username = 'every.one' AND a.answer IS NULL)
OR (q.target_username = 'every.one' AND a.username NOT IN (
SELECT username2
FROM connections
INNER JOIN answers ON answers.username = connections.username2
AND answers.answers IS NOT NULL
WHERE username1 = 'mikha'
))
GROUP BY q.id,a.username
我认为规则4和规则6有点相互对立(可以说是矛盾的),当在一个查询中使用时,它会产生与省略相同的效果......
我没有测试任何查询,但我相信它们有效.
问题是，在某些情况下，当只有一个匹配的答案存在时，您希望将问题显示两次。我引用：
因此，我只想为“mikha”显示一次，无论是否回答，并在每次“mikha”关注的人回答时再次显示
这种重复使事情变得非常困难。
我尝试用 a 解决这个问题UNION，它似乎有效。不过，我还没有完全理解你的要求......
无论如何，我们开始吧：
select * from
(
select
q.id as q_id, a.id as a_id, q.asker_username,
q.target_username, a.username, q.question, a.answer
from
questions q
left outer join answers a on q.id = a.id
where
q.asker_username <> 'mikha'
and
(
q.target_username = 'mikha'
or q.target_username in
(select username2 from connections where username1 = 'mikha')
or
(
q.target_username = 'every.one'
and
(
a.username = 'mikha'
or a.username in
(select username2 from connections where username1 = 'mikha')
or a.id is null
)
)
)
union
select
q.id as q_id, NULL as a_id, q.asker_username,
q.target_username, NULL, q.question, NULL
from
questions q
where
q.asker_username <> 'mikha'
and q.target_username = 'every.one'
and not exists (select id
from answers
where
id = q.id
and username = 'mikha'
)
) r
order by q_id;
现场测试：
有 mikha 对问题 8 的回答
没有 mikha 对问题 8 的回答