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如何从三个表中获取特定记录

发布于 2024-08-18 17:18:09 字数 550 浏览 3 评论 0原文

表名 :: Feedback_master

字段 1. feed_id 2. roll_id 3. batch_id 4. sem_id（学期 ID） 5.f_id（教师 ID） 6. sub_id（科目 ID） 7. 备注。 8. b_id

表名::subject_master

Fields

sub_id(学科ID)
sub_name(学科名称0
f_id(Faculty ID)

表名::faculty_master

Fields

f_id(Faculty Id)
f_name(Faculty Name)
l_name(Faculty Name)
b_id

这是三个表现在我想从这三个表中获取详细信息，

我希望输出为

f_Name（教师名称）、Sub_name（主题名称）和备注（备注）。

当我给出（教师 ID）f_id 时，克服这个问题。

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一生独一 2024-08-25 17:18:09

使用对象

Select T1.f_name, T2.sub_name, T3.remark from faculty_master as T1, 
subject_master as T2, Feedback_master as T3 where T1.f_id = 'your faculty_id'
and T1.f_id = T3.f_id and T2.sub_id = T3.sub_id

Using Objects

Select T1.f_name, T2.sub_name, T3.remark from faculty_master as T1, 
subject_master as T2, Feedback_master as T3 where T1.f_id = 'your faculty_id'
and T1.f_id = T3.f_id and T2.sub_id = T3.sub_id

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等数载，海棠开 2024-08-25 17:18:09

嘿，我猜是MySQL？

SELECT f_name, sub_name, remark 
FROM faculty_master
LEFT JOIN subject_master USING(f_id)
LEFT JOIN Feedback_master USING(f_id)
WHERE f_id = the_id_you_want

heu, MySQL I presume?

SELECT f_name, sub_name, remark 
FROM faculty_master
LEFT JOIN subject_master USING(f_id)
LEFT JOIN Feedback_master USING(f_id)
WHERE f_id = the_id_you_want

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清风夜微凉 2024-08-25 17:18:09

选择 fm.f_name、sm.sub_name、favorite_master fm left 的备注
在 fm.f_id=sm.f_id 上加入 sub_master sm
左加入feedback_master fbm on
sm.sub_id = fbm.sub_id
其中 fm.f_id=123

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酒废 2024-08-25 17:18:09

您可以分阶段构建查询。首先，您需要一份反馈意见列表，因此从这个简单的开始选择查询：

SELECT * FROM Feedback_master

这列出了来自各地的所有反馈，但您希望将其限制为仅针对特定教师的反馈，因此让我们添加一个Where 子句：

SELECT * FROM Feedback_master
  WHERE Feedback_master.f_id = @f_id

现在我们得到了正确的记录列表，但字段列表是错误的。您需要教师姓名和学科名称，而 Feedback_master 表中没有这些信息； subject_master 和 coach_master 表是链接的，假设每个评论都有一个主题 ID 和一个教员 ID，我们可以使用一个简单的内连接来链接表：

SELECT * FROM Feedback_master
  INNER JOIN subject_master ON Feedback_master.sub_id = subject_master.sub_id
  INNER JOIN faculty_master ON Feedback_master.f_id = faculty_master.f_id
  WHERE Feedback_master.f_id = @f_id

现在它从所有三个表中提取所有字段；这包括我们需要的所有字段，因此我们现在可以简单地在 Select 子句中命名它们：

SELECT
  faculty_master.f_name, subject_master.sub_name, Feeback_master.remark
FROM Feedback_master
  INNER JOIN subject_master ON Feedback_master.sub_id = subject_master.sub_id
  INNER JOIN faculty_master ON Feedback_master.f_id = faculty_master.f_id
WHERE Feedback_master.f_id = @f_id

You can build up the query in stages. The first thing is that you're after a list of feedback remarks, so start with this simple select query:

SELECT * FROM Feedback_master

That's listing all the feedback from all over, but you want to limit it to only feedback on a particular faculty, so let's add a Where clause:

SELECT * FROM Feedback_master
  WHERE Feedback_master.f_id = @f_id

Now we've got the right list of records, but the list of fields is wrong. You want the faculty name and subject name, which aren't there in the Feedback_master table; the subject_master and faculty_master tables are linked and assuming that every remark has a subject ID and a faculty ID, we can use a simple inner join to link the tables:

SELECT * FROM Feedback_master
  INNER JOIN subject_master ON Feedback_master.sub_id = subject_master.sub_id
  INNER JOIN faculty_master ON Feedback_master.f_id = faculty_master.f_id
  WHERE Feedback_master.f_id = @f_id

Now it's pulling out all the fields from all three table; this includes all the fields we need, so we can now simply name them in the Select clause:

SELECT
  faculty_master.f_name, subject_master.sub_name, Feeback_master.remark
FROM Feedback_master
  INNER JOIN subject_master ON Feedback_master.sub_id = subject_master.sub_id
  INNER JOIN faculty_master ON Feedback_master.f_id = faculty_master.f_id
WHERE Feedback_master.f_id = @f_id

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