GROUP_CONCAT-位置条件

Question

select group_concat(bookgenre), author_authorID
from Written
group by author_authorID;

gives me

table

group_conat(bookgenre)      author_authorID
Fiction                     123450
Fiction, History            123451
History                     123457
Sci-Fi                      123458
Fiction                     123459

I dont know how to only generation

group_concat(bookgenre)     author_authorID
Fiction                     123450
Fiction                     123459

When I add the condition

where "group_concat(bookgenre)" like 'Fiction'

It results with 0 rows returned

Answer 1

Group_concat is an aggregated function so you should filter using having and not where
And for like you should use wildchar %

select group_concat(bookgenre), author_authorID
from Written
group by author_authorID;
havine group_concat(bookgenre) LIKE '%fiction%'

Answer 2

You can do so by

select group_concat(bookgenre), author_authorID
from Written
group by author_authorID;
having count(*) = sum(bookgenre = 'Fiction')

or use having clause to filter result of aggregate functions

select group_concat(bookgenre), author_authorID
from Written
group by author_authorID;
having group_concat(bookgenre) = 'Fiction'