| SQL functionsExamplesFor each book, find age of author on publication date
jao=# select name, title, (to_date(year::varchar, 'YYYY') - birth_date) / 365
jao-# from author join book using(author_id);
        name        |          title          | ?column? 
--------------------+-------------------------+----------
 Kurt Vonnegut Jr.  | Cat's Cradle            |       40
 Kurt Vonnegut Jr.  | Slaughterhouse Five     |       46
 Kurt Vonnegut Jr.  | Mother Night            |       39
 John Kennedy Toole | A Confederacy of Dunces |       42
 Margaret Atwood    | The Handmaid's Tale     |       46
 Margaret Atwood    | The Testaments          |       80
 Hannah Orenstein   | Playing With Matches    |       25
 Hannah Orenstein   | Love at First Like      |       26
 Hannah Orenstein   | Head Over Heels         |       27
(9 rows)
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