日日操夜夜添-日日操影院-日日草夜夜操-日日干干-精品一区二区三区波多野结衣-精品一区二区三区高清免费不卡

MySQL UNION 運算符可以組合兩個或多個結果集，因此我們可以使用 UNION 運算符創(chuàng)建一個包含多個表數(shù)據(jù)的視圖。為了理解這個概念，我們使用具有以下數(shù)據(jù)的基表“Student_info”和“Student_detail” –

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)

mysql> Select * from Student_detail;
+-----------+-------------+------------+
| Studentid | StudentName | address    |
+-----------+-------------+------------+
|       100 | Gaurav      | Delhi      |
|       101 | Raman       | Shimla     |
|       103 | Rahul       | Jaipur     |
|       104 | Ram         | Chandigarh |
|       105 | Mohan       | Chandigarh |
+-----------+-------------+------------+
5 rows in set (0.00 sec)

登錄后復制

示例

下面的查詢將使用上述兩個表中的數(shù)據(jù)創(chuàng)建一個視圖 –

mysql> Create or Replace View Info AS Select StudentName from Student_detail UNION Select Name From Student_info;
Query OK, 0 rows affected (0.10 sec)

mysql> select * from info;
+-------------+
| StudentName |
+-------------+
| Gaurav      |
| Raman       |
| Rahul       |
| Ram         |  
| Mohan       |
| YashPal     |
| Shyam       |
+-------------+
7 rows in set (0.00 sec)

登錄后復制

上面的結果集包含兩列中的值的組合。如果一個值重復，那么它會消除重復的值。

我們還可以存儲所有值，也可以通過使用 UNION ALL 來重復一個值，如以下查詢所示 –

mysql> Create or Replace View Info AS Select student name from Student_detail UNION ALL Select Name From Student_info;
Query OK, 0 rows affected (0.16 sec)

mysql> select * from info;
+-------------+
| StudentName |
+-------------+
| Gaurav      |
| Raman       |
| Rahul       |
| Ram         |
| Mohan       |
| YashPal     |
| Gaurav      |
| Raman       |
| Ram         |
| Shyam       |
| Mohan       |
+-------------+
11 rows in set (0.00 sec)

登錄后復制

以上就是如何使用多個表中的數(shù)據(jù)創(chuàng)建 MySQL 視圖？的詳細內容，更多請關注www.92cms.cn其它相關文章！