postgresql数据库-PostgreSQL模式Schema

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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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