PostgreSQL模式Schema

2019年10月3日 201次阅读

模式（schema）实际上一个命名表的集合。也可以包含一个schema视图，索引，序列，数据类型，运算符和函数。Schema是满足类似于在操作系统级别的目录，但该模式不能嵌套。 CREATE SCHEMA PostgreSQL语句创建一个模式（schema）。

语法

创建型模式的基本语法如下：

CREATE SCHEMA name;

其中，name是模式的名称。

在Schema中创建表的语法

The basic syntax to create table in schema is as follows:

CREATE TABLE myschema.mytable (
...
);

Example

Let us see an example for creating a schema. Connect to the database testdb and create a schemamyschema as follows:

testdb=# create schema myschema;
CREATE SCHEMA

The message “CREATE SCHEMA” signifies that the schema is created successfully.

Now, let us create a table in the above schema as follows:

testdb=# create table myschema.company(
   ID   INT              NOT NULL,
   NAME VARCHAR (20)     NOT NULL,
   AGE  INT              NOT NULL,
   ADDRESS  CHAR (25) ,
   SALARY   DECIMAL (18, 2),
   PRIMARY KEY (ID)
   );

This will create an empty table. You can verify the table created with the command below:

testdb=# select * from myschema.company;

This would produce following result:

 id | name | age | address | salary
----+------+-----+---------+--------
(0 rows)

删除模式语法

To drop a schema if it’s empty (all objects in it have been dropped), then use:

DROP SCHEMA myschema;

To drop a schema including all contained objects, use:

DROP SCHEMA myschema CASCADE;

使用模式的优势

  • It allows many users to use one database without interfering with each other.

  • It organizes database objects into logical groups to make them more manageable.

  • Third-party applications can be put into separate schemas so they do not collide with the names of other objects.

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