Question

SELECT user.login, book.name
FROM user
LEFT JOIN book ON
user.login = book.author
WHERE user.login = ‘peter’

Now i get:

peter book1
peter book2
peter book2

Bu i wish get:

peter book1
      book2
      book2

Database: MySQL
Thanks

Answer 1

I agree with others that while this is something that can be performed in SQL, it really shouldn’t be.

The following assumes that there can be only one author per book, which is not the case in reality:

SELECT x.author,
       x.book_name
  FROM (SELECT CASE 
                 WHEN @author != u.login THEN u.login
                 ELSE ''
               END AS author, 
               b.name AS book_name,
               @author := u.login AS set_variable  
          FROM USER u
     LEFT JOIN BOOK b ON b.author = u.login
          JOIN (SELECT @author := '') r
         WHERE u.login = 'peter'
      ORDER BY u.login) x

It uses a variable (only MySQL supports this, to my knowledge) to store the author/login value. The CASE expression is set to return the column value if it does not match what is currently stored in the variable. If the variable and the column value match, a zero length string will occupy the column value – you could change this to be NULL if you like.

I included an ORDER BY in the likelihood you’d want this to happen for multiple names, because there’s no way to guarantee data order without an ORDER BY.

I had to use a subquery, otherwise, the column where the variable gets set would appear in your resultset.