从另一个表获取记录

Question

I'm trying to read all of my data, but there is one record that is in another table. Can I read it together with my other records in one query?

 $sql_query="SELECT * FROM blog_posts ORDER BY id DESC";

// table to display results here // modify here 
echo '<h1>'.$rows["title"].'</p></h1>';
echo '<p> '.$rows["post"].'</p>';
echo '<p><span class="style1">Door</span>: '.$rows["first_name"].' ';
echo '<p>Geplaatst op</span>: '.$rows["date_posted"].'</p>';                           
echo "<BR>";

The record: first_name is comming from the table: people. The rest is all from blog_posts.

Answer 1

Use LEFT JOIN in your query like this

SELECT * FROM blog_posts
LEFT JOIN people
ON blog_posts.{USERIDCOLUMNNAME}=people.{USERIDCOLUMNNAME}
ORDER BY blog_posts.id DESC; 

Or like Raul posted in his comment define every column:

SELECT people.name as name, blog_posts.title as title, blog_posts.post as post FROM blog_posts,people WHERE blog_posts.people_id=people.id ORDER BY id DESC 

Answer 2

Call me crazy, but it looks like first_name is a field in another table and not an entire record. Therefore I think the approach you're looking for is to join your blog_posts table with your people table. How you go about that, though completely depends on the relationship: one-to-one, one-to-many, or many-to-many.

If it's one to one (which it probably isn't), then you most likely have a foreign key to the other table in both tables (ie there is a blog_post.people_id field and a people.blog_post_id field). If this is the case, then it doesn't matter which way you perform the join. Since you're already selecting from the blog_posts table, then it could look like this:

SELECT * FROM blog_posts
    INNER JOIN people ON blog_posts.people_id = people.id

Note that using the * in this manner when selecting will select all fields from both tables (not what you want, most likely).

For one-to-many, there is only a single foreign key on one of your tables. This is probably your case: one person can author many articles, and the relationship is stored in the field blog_posts.person_id. In this case, the query above is exactly the same. The only difference is you can't go the other way

For a many-to-many relationship, you would have to have a join table in the middle between the two tables (some people refer to these as 'pivot' tables). This table would only need to record both the people_ids and the blog_post_ids, and represents a situation where you would allow for many people to author a single blog post, and a single person to also be an author for many blog posts. The query for this relationship would be different:

SELECT * FROM blog_posts b
    INNER JOIN blog_post_people bp ON bp.blog_post_id = b.blog_post_id
    INNER JOIN people p ON p.people_id = bp.people_id

Again, using the * here when selecting will give you the columns from all three tables, and you should probably avoid using it.

Answer 3

您可以从多个表格中进行选择

$sql_query="SELECT * FROM blog_posts,people WHERE people.id=$id"; ORDER BY id DESC