Auto commit

2208/天天乐学考试答案/MySQL练习（一）.md

@@ -230,13 +230,19 @@ FROM tb_books b;
 UPDATE tb_books b
 SET b.note = SUBSTR(b.note,INSTR(b.note,'-')+2);
 
-#7 tj11
+#7 tj11 多表连接+条件+排序
 SELECT b.book_id, b.title, a.author_id, a.author_name, b.publication_date
 FROM tb_books b, tb_authors a
 WHERE b.note = a.author_name  AND YEAR(b.publication_date) BETWEEN 1980 AND 2010
 ORDER BY b.publication_date DESC;
 
-#8
+#8 tj12 多表连接+分组+分组后条件
+SELECT a.author_id, a.author_name, COUNT(*)
+FROM tb_books b, tb_authors a
+WHERE b.note = a.author_name
+GROUP BY a.author_id
+HAVING COUNT(*) > 1;
+
 
 #9
 ```