php / sql连接多个字段的表

Question

I'm trying to echo info from a database onto the webpage. The page is supposed to have a bunch of article publications which includes the title, authors, journal name (if applicable), date published. For example:

1. title of the article (with author 1, author 2, author 3), name of the journal, date published.

I've made two tables. One contains paper_id, author_id, paper_name, journal_name, date. Second one contains author_id, author_firstname, author_lastname.

The part I'm struggling with is outputting multiple authors. in the second table I have the following for first paper

author_id: 1
author_firstname: john
author_lastname: smith

author_id: 1
author_firstname: bob
author_lastname: thomas

I want to print this: Name of the paper (with john smith, bob thomas), journal name, date published.

I've tried joining author_id but it outputs the same paper twice (since i have two authors with id 1. I need suggestions as to how i should change the table or join it differently and what not. Any help will be appreciated, thanks. I'm also a beginner programmer

Answer 1

I beleieve the correct strategy is to use GROUP_CONCAT on each paper to obtain a comma separated list of authors. As a note, each group in the query below having a given paper_id will also have the same values for paper_name, journal_name and date. I include the columns other than paper_id so that they will be available in the SELECT clause.

SELECT t1.paper_name,
    GROUP_CONCAT(CONCAT(t2.author_lastname, ', ', t2.author_firstname)
    SEPARATOR ' '),
    t1.journal_name, t1.date
FROM table1 t1 INNER JOIN table2 t2
ON t1.author_id = t2.author_id
GROUP BY t1.paper_id, t1.paper_name, t1.journal_name, t1.date