add datatypes and logical operators

Author: ptyadana

Diff for: 09. Aggregate Functions.sql

@@ -11,4 +11,117 @@ FROM books;
 
 /*How many titles contain "the"?*/
 SELECT COUNT(*) FROM books
-WHERE title LIKE '%the%'
+WHERE title LIKE '%the%';
+
+/*COUNT how many books each author has written*/
+SELECT CONCAT(author_fname,' ',author_lname) AS 'author name',COUNT(*) AS 'number of books'
+FROM books
+GROUP BY 1
+ORDER BY 2 DESC;
+
+
+/*books count by released years*/
+SELECT released_year, COUNT(*) AS 'number of books'
+FROM books
+GROUP BY released_year
+ORDER BY released_year DESC;
+
+
+/*Find the minimum released_year*/
+SELECT MIN(released_year) FROM books;
+
+/*Find the longest book (but took long as 2 quries have to run)*/
+SELECT *
+FROM books
+WHERE pages = (SELECT MAX(pages) FROM books);
+
+/* Faster way */
+SELECT * FROM books
+ORDER BY pages DESC
+LIMIT 1;
+
+
+/*Find the year each author published their first book*/
+SELECT author_fname,author_lname,MIN(released_year)
+FROM books
+GROUP BY 1,2;
+
+/*Find the longest page count for each author*/
+SELECT author_fname,author_lname,MAX(pages)
+FROM books
+GROUP BY 1,2;
+
+
+/*Sum all pages in the entire database*/
+SELECT SUM(pages) FROM books;
+
+/*Sum all pages each author has written*/
+SELECT author_fname,author_lname,SUM(pages)
+FROM books
+GROUP BY author_fname,author_lname;
+
+
+/*Calculate the average released_year across all books*/
+SELECT AVG(released_year) FROM books;
+
+
+/*Calculate the average stock quantity for books released in the same year*/
+SELECT released_year, AVG(stock_quantity)
+FROM books
+GROUP BY released_year;
+
+/*-----------------------------------------------------------*/
+
+/*-------------- Challenges --------------------------------*/
+/*Print the number of books in the database*/
+SELECT COUNT(*) AS 'number of books' FROM books;
+
+
+/*Print out how many books were released in each year*/
+SELECT released_year, COUNT(*) as 'number of books'
+FROM books
+GROUP BY released_year;
+
+
+/*Print out the total number of books in stock*/
+SELECT SUM(stock_quantity) AS 'total number books in stock'
+FROM books;
+
+
+/*Find the average released_year for each author*/
+SELECT author_fname,author_lname,AVG(released_year)
+FROM books
+GROUP BY author_fname,author_lname;
+
+
+/*Find the full name of the author who wrote the longest book*/
+SELECT CONCAT(author_fname,' ',author_lname) AS 'Author Full Name', title, pages
+FROM books
+ORDER BY pages DESC
+LIMIT 1;
+
+/*
++------+---------+-----------+
+| year | # books | avg pages |
++------+---------+-----------+
+| 1945 |       1 |  181.0000 |
+| 1981 |       1 |  176.0000 |
+| 1985 |       1 |  320.0000 |
+| 1989 |       1 |  526.0000 |
+| 1996 |       1 |  198.0000 |
+| 2000 |       1 |  634.0000 |
+| 2001 |       3 |  443.3333 |
+| 2003 |       2 |  249.5000 |
+| 2004 |       1 |  329.0000 |
+| 2005 |       1 |  343.0000 |
+| 2010 |       1 |  304.0000 |
+| 2012 |       1 |  352.0000 |
+| 2013 |       1 |  504.0000 |
+| 2014 |       1 |  256.0000 |
+| 2016 |       1 |  304.0000 |
+| 2017 |       1 |  367.0000 |
++------+---------+-----------+
+*/
+SELECT released_year AS 'year' ,COUNT(*) AS '# books', AVG(pages) AS 'avg pages'
+FROM books
+GROUP BY released_year;