PostgreSQL - Schema

Quiz

A schema is a named collection of tables. A schema can also contain views, indexes, sequences, data types, operators, and functions. Schemas are like folders in an operating system, but they can't contain other schemas inside them. PostgreSQL statement CREATE SCHEMA creates a schema.

Syntax

Following is the basic syntax of CREATE SCHEMA is as follows −

CREATE SCHEMA name;

Here,

name is the name of the schema.

Syntax for Creating a Table in Schema

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 schema myschema 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 given below −

testdb=# select * from myschema.company;

This would produce the following result −

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

Syntax of Drop Schema

To drop a schema if it is empty (all objects in it have been dropped), use the command −

DROP SCHEMA myschema;

To drop a schema including all contained objects, use the command −

DROP SCHEMA myschema CASCADE;

Listing all PostgreSQL Schemas

To listing all the schemas in SQL shell (psql), use the following command −

postgres=# \dt *.*;

The above command produces the following result −

On using "\dn+" command helps you to get the schemas list in details like access privileges and description. Here is the given screenshots of the command and its result.

Advantages of using a Schema

Following are the list of points describe about advantages of using schemas −

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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