sql视图

An interesting thing you can do with SQL is to create a view.

使用SQL可以做的一件有趣的事情是创建一个视图 。

A view is like a table, except instead of being a real table, on its own, it is dynamically built by the result of a SELECT query.

视图就像一个表，除了它本身不是真实的表之外，它是由SELECT查询的结果动态构建的。

Let’s use the example we used in the joins lesson:

让我们使用在连接课程中使用的示例：

CREATE TABLE people (  age INT NOT NULL,  name CHAR(20) NOT NULL PRIMARY KEY);CREATE TABLE cars (  brand CHAR(20) NOT NULL,  model CHAR(20) NOT NULL,  owner CHAR(20) NOT NULL PRIMARY KEY);

We add some data:

我们添加一些数据：

INSERT INTO people VALUES (37, 'Flavio');INSERT INTO people VALUES (8, 'Roger');INSERT INTO cars VALUES ('Ford', 'Fiesta', 'Flavio');INSERT INTO cars VALUES ('Ford', 'Mustang', 'Roger');

We can create a view that we call car_age that always contains the correlation between a car model and its owner’s age:

我们可以创建一个称为car_age的视图，该视图始终包含汽车模型与其所有者年龄之间的相关性：

CREATE VIEW car_age AS SELECT model, age AS owner_age FROM people JOIN cars ON people.name = cars.owner;

Here is the result we can inspect with SELECT * FROM car_age:

这是我们可以使用SELECT * FROM car_age检查的结果：

model         | owner_age ----------------------+----------- Fiesta               |        37 Mustang              |         8

The view is persistent, and will look like a table in your database. You can delete a view using DROP VIEW:

该视图是持久性的，看起来像数据库中的表。 您可以使用DROP VIEW删除DROP VIEW ：

DROP VIEW car_age

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sql视图