MySQL 如何创建一个空视图
要在MySQL中创建一个空视图,请以下面的语法为准-
create or replace view yourViewName as
select yourValue AS yourColumnName,
yourValue AS yourColumnName2,
.
.
N
from dual
where false;
Mysql
实现上述语法以创建MySQL中的空视图 –
mysql> create or replace view empty_view as
select "John Smith" AS ClientName,
"US" AS ClientCountryName,
false AS isMarried
from dual
where false;
Query OK, 0 rows affected (0.20 sec)
Mysql
检查视图描述 –
mysql> desc empty_view;
Mysql
将产生以下输出 –
+-------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+-------------+------+-----+---------+-------+
| ClientName | varchar(10) | NO | | | |
| ClientCountryName | varchar(2) | NO | | | |
| isMarried | int(1) | NO | | 0 | |
+-------------------+-------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
Mysql
检查视图是否为空 –
mysql> select *from empty_view;
Empty set (0.00 sec)
Mysql
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