介绍
View是一个数据库对象，它在一个或多个表中显示数据。用于创建视图的相同SQL语句也可用于替换现有视图。
本指南将使用略有不同且名称不同的视图更新（替换）现有视图“programming-students-v”。
安全提示：在对模式进行更改之前始终备份模式。
一般语法
CREATE OR REPLACE VIEW view_name AS
SELECT column1, column2, ...
FROM table_name
WHERE condition;
SQL用于创建视图和当前数据
create view `programming-students-v` as
select FullName, programOfStudy
from student
where programOfStudy = 'Programming';
select * from `programming-students-v`;
当前数据：
+-----------------+----------------+
| FullName | programOfStudy |
+-----------------+----------------+
| Teri Gutierrez | Programming |
| Spencer Pautier | Programming |
| Louis Ramsey | Programming |
| Alvin Greene | Programming |
| Sophie Freeman | Programming |
+-----------------+----------------+
5 rows in set (0.00 sec)
现有视图的列表：
SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';
+-----------------------------------+------------+
| Tables_in_fcc_sql_guides_database | Table_type |
+-----------------------------------+------------+
| programming-students-v | VIEW |
| students-contact-info_v | VIEW |
| students_dropme_v | VIEW |
+-----------------------------------+------------+
3 rows in set (0.00 sec)
替换视图
create or replace view `programming-students-v` as
select FullName, programOfStudy, sat_score
from student
where programOfStudy = 'Programming';
select * from `programming-students-v`;
注意：视图现在显示sat_score。
+-----------------+----------------+-----------+
| FullName | programOfStudy | sat_score |
+-----------------+----------------+-----------+
| Teri Gutierrez | Programming | 800 |
| Spencer Pautier | Programming | 1000 |
| Louis Ramsey | Programming | 1200 |
| Alvin Greene | Programming | 1200 |
| Sophie Freeman | Programming | 1200 |
+-----------------+----------------+-----------+
注意：视图列表没有更改，我们的视图被替换。
mysql> SHOW FULL TABLES IN fcc_sql_guides_database WHERE TABLE_TYPE LIKE 'VIEW';
+-----------------------------------+------------+
| Tables_in_fcc_sql_guides_database | Table_type |
+-----------------------------------+------------+
| programming-students-v | VIEW |
| students-contact-info_v | VIEW |
| students_dropme_v | VIEW |
+-----------------------------------+------------+
3 rows in set (0.00 sec)
*与所有这些SQL事物一样，它们比本入门指南中的内容更多。我希望这至少足以让你开始。请参阅您的数据库管理员手册，并自己尝试不同的选项。
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