sql - Getting a "not a single-group group function" error, tried researching it -


i'm taking database summer course i'm new @ this. here code. i'm trying display average price each type of book in database. 

select distinct type, avg(price) average_price  book  order type;

the error because trying select data (type) in grouped query. avg function causes query grouped, whole result single group haven't specified group by.

to average each type of book, need group on type:

select type, avg(price) average_price book group type order type;

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