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2208/天天乐学考试答案/MySQL练习（一）.md

@@ -243,7 +243,21 @@ WHERE b.note = a.author_name
 GROUP BY a.author_id
 HAVING COUNT(*) > 1;
 
+#9 视图
+CREATE VIEW v_book AS
+SELECT b.genre, a.author_name, COUNT(*) c
+FROM tb_books b, tb_authors a
+WHERE b.note = a.author_name
+GROUP BY b.genre, a.author_id 
+HAVING COUNT(*) = (
+	SELECT COUNT(*)
+	FROM tb_books
+	WHERE b.genre = genre
+	GROUP BY note
+	ORDER BY COUNT(*) DESC
+	LIMIT 1
+);
+
 
-#9
 ```