Retrieve user id for users that have 5 specific rows
If your both tables have referential relationship with entry_id then you can fetch your result data through with 'IN' clause. 
No need to write down as many AND operator in the query.

select t.author_id,t.entry_id,d.entry_id

from yourdatabsename.titles as t left outer join yourdatabasename.data  as d

on t.entry_id=d.entry_id

where d.skills IN ('Skill A','Skill B','Skill C','Skill D','Skill E')

Group By t.author_id

Order By t.author_id
;