Databases
StackOverflow2013
Postsdbo
POMySQL: joining a lot of tables
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POMySQL: joining a lot of tables
    primarykey
    data
    text
    <p>I have these tables in my MySQL database for a simple college library application (I simplified them a little bit for obvious reasons):</p> <pre><code>SELECT * FROM language; ╔═════════════╦══════════╗ ║ language_id ║ language ║ ╠═════════════╬══════════╣ ║ 11 ║ English ║ ║ 12 ║ Russian ║ ║ 13 ║ German ║ ╚═════════════╩══════════╝ SELECT * FROM subject; ╔════════════╦═════════════╗ ║ subject_id ║ subject ║ ╠════════════╬═════════════╣ ║ 21 ║ Mathematics ║ ║ 22 ║ History ║ ║ 23 ║ Chemistry ║ ║ 24 ║ Physics ║ ╚════════════╩═════════════╝ SELECT publisher_id, publisher FROM publisher; ╔══════════════╦═══════════════╗ ║ publisher_id ║ publisher ║ ╠══════════════╬═══════════════╣ ║ 31 ║ Berkley Books ║ ║ 32 ║ Penguin ║ ╚══════════════╩═══════════════╝ SELECT author_id, first_name, last_name FROM author; ╔═══════════╦════════════╦═══════════╗ ║ author_id ║ first_name ║ last_name ║ ╠═══════════╬════════════╬═══════════╣ ║ 41 ║ Joe ║ Schmoe ║ ║ 42 ║ John ║ Smith ║ ╚═══════════╩════════════╩═══════════╝ SELECT book_id, title, language_id, subject_id, publisher_id FROM book; ╔═════════╦═══════╦═════════════╦════════════╦══════════════╗ ║ book_id ║ title ║ language_id ║ subject_id ║ publisher_id ║ ╠═════════╬═══════╬═════════════╬════════════╬══════════════╣ ║ 1 ║ A ║ 11 ║ 22 ║ 31 ║ ║ 2 ║ B ║ 13 ║ 24 ║ 32 ║ ╚═════════╩═══════╩═════════════╩════════════╩══════════════╝ SELECT book_id, author_id FROM book_author; ╔═════════╦════════════╗ ║ book_id ║ author_id ║ ╠═════════╬════════════╣ ║ 1 ║ 41 ║ ║ 1 ║ 42 ║ ║ 2 ║ 41 ║ ╚═════════╩════════════╝ SELECT book_copy_id, book_id FROM book_copy; ╔══════════════╦═════════╗ ║ book_copy_id ║ book_id ║ ╠══════════════╬═════════╣ ║ 1 ║ 1 ║ ║ 2 ║ 1 ║ ║ 3 ║ 1 ║ ║ 4 ║ 2 ║ ║ 5 ║ 2 ║ ╚══════════════╩═════════╝ </code></pre> <p>I have one query that looks like this (I'm showing it to you just in case):</p> <pre><code>SELECT b.book_id, b.title, GROUP_CONCAT(CONCAT_WS(' ', a.last_name, a.first_name) ORDER BY a.last_name SEPARATOR ', ') AS authors, l.language, s.subject, p.publisher FROM book AS b LEFT JOIN book_author AS ba ON b.book_id = ba.book_id LEFT JOIN author AS a ON ba.author_id = a.author_id LEFT JOIN language AS l ON b.language_id = l.language_id LEFT JOIN subject AS s ON b.subject_id = s.subject_id LEFT JOIN publisher AS p ON b.publisher_id = p.publisher_id GROUP BY b.title ASC; ╔═════════╦═══════╦════════════════════════╦══════════╦═════════╦═══════════════╗ ║ book_id ║ title ║ authors ║ language ║ subject ║ publisher ║ ╠═════════╬═══════╬════════════════════════╬══════════╬═════════╬═══════════════╣ ║ 1 ║ A ║ Joe Schmoe, John Smith ║ English ║ History ║ Berkley Books ║ ║ 2 ║ B ║ John Smith ║ German ║ Physics ║ Penguin ║ ╚═════════╩═══════╩════════════════════════╩══════════╩═════════╩═══════════════╝ </code></pre> <p>Now, I would like to have this selection:</p> <pre><code>╔══════════════╦═══════╦════════════════════════╦══════════╦═════════╦═══════════════╗ ║ book_copy_id ║ title ║ authors ║ language ║ subject ║ publisher ║ ╠══════════════╬═══════╬════════════════════════╬══════════╬═════════╬═══════════════╣ ║ 1 ║ A ║ Joe Schmoe, John Smith ║ English ║ History ║ Berkley Books ║ ║ 2 ║ A ║ Joe Schmoe, John Smith ║ English ║ History ║ Berkley Books ║ ║ 3 ║ A ║ Joe Schmoe, John Smith ║ English ║ History ║ Berkley Books ║ ║ 4 ║ B ║ John Smith ║ German ║ Physics ║ Penguin ║ ║ 5 ║ B ║ John Smith ║ German ║ Physics ║ Penguin ║ ╚══════════════╩═══════╩════════════════════════╩══════════╩═════════╩═══════════════╝ </code></pre> <p>I also have these two tables:</p> <pre><code>SELECT student_id, first_name, last_name FROM student; ╔════════════╦════════════╦═══════════╗ ║ student_id ║ first_name ║ last_name ║ ╠════════════╬════════════╬═══════════╣ ║ 81 ║ Bob ║ Dylan ║ ║ 82 ║ Jim ║ Carrey ║ ╚════════════╩════════════╩═══════════╝ SELECT student_id, book_copy_id FROM loan; ╔════════════╦══════════════╗ ║ student_id ║ book_copy_id ║ ╠════════════╬══════════════╣ ║ 81 ║ 1 ║ ║ 81 ║ 4 ║ ║ 82 ║ 5 ║ ╚════════════╩══════════════╝ </code></pre> <p>I need to write a query that produces this selection:</p> <pre><code>-- 'a' stands for 'the quantity of book copies that are available for a loan' -- 't' stands for 'the total quantity of book copies' ╔═══╦═══╦═══════╦════════════════════════╦══════════╦═════════╦═══════════════╗ ║ a ║ t ║ title ║ authors ║ language ║ subject ║ publisher ║ ╠═══╬═══╬═══════╬════════════════════════╬══════════╬═════════╬═══════════════╣ ║ 2 ║ 3 ║ A ║ Joe Schmoe, John Smith ║ English ║ History ║ Berkley Books ║ ║ 0 ║ 2 ║ B ║ John Smith ║ German ║ Physics ║ Penguin ║ ╚═══╩═══╩═══════╩════════════════════════╩══════════╩═════════╩═══════════════╝ </code></pre> <p>I hope I have been quite explicit outlining it with diagrams. Please, hemp me out with writing queries for these two problems.</p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USMikhail
    1. USMikhail
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POMySQL: joining a lot of tables
      1. This table or related slice is empty.
      1. VTUpMod
    1. CO+1 just for your ascii art :-D Btw you should also put a copy on [sqlfiddle](http://sqlfiddle.com/). So it's simper to help you.
      singulars
      1. POMySQL: joining a lot of tables
      1. USrekire
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload