我们可以使用GROUP BY对列中的值进行分组，并且如果需要，我们可以对该列执行计算。您可以在分组列上使用 COUNT、SUM、AVG 等函数。为了理解带有视图的 GROUP BY 子句，我们使用具有以下数据的基表“Student_info”创建一个名为“Info”的视图 –
mysql> Select * from Student_info;+------+---------+------------+------------+| id | Name | Address | Subject |+------+---------+------------+------------+| 101 | YashPal | Amritsar | History || 105 | Gaurav | Chandigarh | Literature || 125 | Raman | Shimla | Computers || 130 | Ram | Jhansi | Computers || 132 | Shyam | Chandigarh | Economics || 133 | Mohan | Delhi | Computers |+------+---------+------------+------------+6 rows in set (0.00 sec)
语法
Create or Replace View view_name AS Select_statements FROM table GROUP BY expression1, expression2, ... expression_n;
示例
mysql> Create or Replace View Info AS select Subject, COUNT(*) FROM Student_info GROUP BY Subject;Query OK, 0 rows affected (0.10 sec)mysql> Select * from info;+------------+----------+| Subject | COUNT(*) |+------------+----------+| Computers | 3 || Economics | 1 || History | 1 || Literature | 1 |+------------+----------+4 rows in set (0.00 sec)mysql> Create or Replace View Info AS select Subject,Name, COUNT(Subject) FROM Student_info GROUP BY Subject, Name;Query OK, 0 rows affected (0.05 sec)
上面的查询将在 GROUP BY 子句中包含两列。
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mysql> Select * from info;+------------+---------+----------------+| Subject | Name | COUNT(Subject) |+------------+---------+----------------+| Computers | Mohan | 1 || Computers | Ram | 1 || Computers | Raman | 1 || Economics | Shyam | 1 || History | YashPal | 1 || Literature | Gaurav | 1 |+------------+---------+----------------+6 rows in set (0.00 sec)
上面的结果集显示，GROUP BY 子句按列的值将一组行分组为一组汇总行。
以上就是我们如何使用 GROUP BY 子句创建 MySQL 视图？的详细内容，更多请关注创想鸟其它相关文章！
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