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This graphic is explained in the accompanying text Domains Locate the document in the library structure

When you create a table, you can define a domain for each column.

 

CREATE TABLE hotel.customer
(cno        
FIXED(4) PRIMARY KEY CONSTRAINT cno_cons CHECK cno > 0,
 title      
CHAR(7)  CONSTRAINT title_cons CHECK title IN ('Mr','Mrs','Company'),
 firstname  
CHAR(20),
 name       
CHAR(20) NOT NULL,
...)

The customer number consists of four digits, the title is seven characters long, and the first and last names are each 10 characters long.

See also:

CREATE TABLE Statement (create_table_statement)

 

You can predefine these domains in a domain definition.

 

Creating a Domain

To create a domain, use the CREATE DOMAIN statement.

 

CREATE DOMAIN name_domain CHAR(20)

Names are to be 20 characters long.

 

CREATE DOMAIN birthday_domain DATE DEFAULT DATE
  CONSTRAINT birthday_domain> '1880-01-01' AND birthday_domain <= DATE

In the domain definition birthday_domain for the birthday, the current date is selected as the DEFAULT value. The birth date is not to be before 01/01/1880.

 

In a domain definition, you can specify a DEFAULT value and/or a CONSTRAINT definition.

·        The DEFAULT values must satisfy any existing restrictive conditions.

·        No constraint name can be specified in the CONSTRAINT definition and the domain is used as the column name.

Using the Domain

...

       1.      If necessary, drop the person table.
DROP TABLE hotel.person

    2.      Create the person table.
CREATE TABLE hotel.person
(pno       FIXED(6) PRIMARY KEY,
 name      name_domain,
 city      CHAR(20))

    3.      Add a  birthday column with the domain birthday_domain .
ALTER TABLE person ADD birthday birthday_domain

The person table was created in accordance with the name_domain domain for names and with the birthday column with the domain definition birthday_domain .

 

See also:

CREATE DOMAIN Statement (create_domain_statement)

Evaluating System Tables, COLUMNS, DOMAINS, DOMAINCONSTRAINTS

 

Dropping a Domain

To drop a domain, use the DROP DOMAIN statement:

 

DROP DOMAIN name_domain

You can use this SQL statement to drop the domain definition. Table definitions that used this domain definition are not dropped.

 

See also:

DROP DOMAIN Statement (drop_domain_statement)

 

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