模式(schema)實際上一個命名表的集合。也可以包含一個schema視圖,索引,序列,數據類型,運算符和函數。Schema是滿足類似於在操作系統級別的目錄,但該模式不能嵌套。 CREATE SCHEMA PostgreSQL語句創建一個模式(schema)。
創建型模式的基本語法如下:
CREATE SCHEMA name;
其中,name是模式的名稱。
The basic syntax to create table in schema is as follows:
CREATE TABLE myschema.mytable ( ... );
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)
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;
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.