How to return first book published by each author?

问题

The question is

For each author, return the title and published_date of their first book. The result set should have five columns: author’s id, author’s name, book’s id, book’s title, and book’s published_date.

So I have the ouput columns I want except its displaying every book by each author with the required items, how do I get it to only show the book with the earliest published_date?

SELECT authors.id, authors.author, books.id, books.title, books.published_date

FROM authors

INNER JOIN books

ON authors.id = books.author_id

回答1:

One way of solving this is to use a query that fetches for each author the min publish date from the table books and then join it to the 2 tables:

select 
  a.id, a.author,
  b.id, b.title, b.published_date
from authors a 
inner join books b on b.author_id = a.id
inner join (
  select author_id, min(published_date) published_date
  from books
  group by author_id
) g on g.author_id = b.author_id and g.published_date = b.published_date

回答2:

If using a recent version of sqlite (3.25 or newer), you can use window functions for a clean approach:

Given this sample database:

CREATE TABLE authors(id INTEGER PRIMARY KEY, author TEXT);
INSERT INTO authors VALUES (1, 'John Steinbeck'), (2, 'William Faulkner');
CREATE TABLE books(id INTEGER PRIMARY KEY
                 , author_id INTEGER REFERENCES authors(id)
                 , title TEXT, published_date TEXT);
INSERT INTO books(author_id, title, published_date) VALUES
 (1, 'The Grapes Of Wrath', '1939-04-14'),
 (2, 'As I Lay Dying', '1930-10-06'),
 (2, 'The Sound And The Fury', '1929-10-07'),
 (1, 'East Of Eden', '1952-09-19'),
 (1, 'Tortilla Flat', '1935-01-01');

this query:

WITH ranked(author_id, author, book_id, title, published_date, published_order) AS
 (SELECT a.id, a.author, b.id, b.title, b.published_date
       , rank() OVER (PARTITION BY a.id ORDER BY b.published_date)
  FROM authors AS a
  JOIN books AS b ON a.id = b.author_id)
SELECT author_id, author, book_id, title, published_date
FROM ranked
WHERE published_order = 1
ORDER BY author_id;

will produce:

author_id   author          book_id     title          published_date
----------  --------------  ----------  -------------  --------------
1           John Steinbeck  5           Tortilla Flat  1935-01-01    
2           William Faulkn  3           The Sound And  1929-10-07

For each author, it assigns a rank to each book in publication order (The rank() OVER (PARTITION BY a.id ORDER BY b.published_date) column calculated in the CTE), and then selects only the books where that rank is 1 for the final results.

来源：https://stackoverflow.com/questions/56244360/how-to-return-first-book-published-by-each-author

标签

sql

sqlite