How to PIVOT SQL key value pairs

I currently have data and I am looking to pivot the data.

CustomerId BookKey BookValue
John       Title   Goosebumps
John       Count   5
Max        Title   Harry Potter
Max        Count   7
Max        Pages   50

After pivot it should look like

CustomerId Title          Count Pages
John       GooseBumps       5     -
Max        Harry Potter     7     50

I can currently achieve this by repeadedly combining with a left join but there’s a ton of rows. Looking for a way that doesn’t involve so many left joins.

select cus.*, db2.BookValue as Title, db3.BookValue as Count, db4.BookValue as Pages
from 
(
    select customerid 
    from data_bags db 
    group by customerid 
) cus
left join databags db2 
    on cus.customerid  = db2.customerid  and db2.BookKey  = 'Title'
left join databags db3 
    on cus.customerid  = db3.customerid  and db3.BookKey  = 'Count'
left join databags db4
    on cus.customerid  = db4.customerid  and db4.BookKey  = 'Pages'

....
....

>Solution :

You could use a case expression each wrapped in max().

select 
 customerId, 
 max(case when bookKey = 'Title' then bookValue end) as title, 
 max(case when bookKey = 'Count' then bookValue end) as count, 
 max(case when bookKey = 'Pages' then bookValue end) as pages
from data_bags
group by customerId;