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New Message on BDOTNET
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From: Atanu-P
Message 1 in Discussion
Hi, there, I need a small help reg SQL, Can anyone suggest 1.What is the
difference between an UserDefindedType DataType and a Domain Type DataType in
SQL. And When to use which?
For example, I can create a type as follows:CREATE TYPE PERSON AS OBJECT (NAME
VARCHAR2(30), SSN VARCHAR2(9));
I can reference your user-defined type as follows:CREATE TABLE EMP_PAY
(EMPLOYEE PERSON, SALARY NUMBER(10,2), HIRE_DATE DATE); And also
I can create a domain as follows:CREATE DOMAIN MONEY_D AS NUMBER(8,2);
I can reference the domain as follows: CREATE TABLE EMP_PAY (EMP_ID
NUMBER(9), EMP_NAME VARCHAR2(30), PAY_RATE MONEY_D); So where is
the difference...? 2. What is the Difference between a Primary Key and Unique
in a database table, except that, Primary key does not accept NULL value where
as Unique Key accepts? Any help highly appreaciated. Thanks
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