SQL Server Interview Question Answers -- Part 2

4) What is Check Constraint?
Check constraint specifies a condition that is enforced for each row of the table on which the constraint is defined. Once constraint is defined, insert or update to the data within the tables is checked against the defined constraint.

6) What is the difference between RULE and Check Constraint?
The major difference between rule and Check is reusability. Check constraint is associated with columns in a Table. So these can't be re-used. Rules are defined with in a database and can be applied to any number of columns.

7) How to create a relationship between two tables?
Using Foreign Keys. Create a Foreign Key on child table referencing Unique Key or Primary key of Parent table.

8) Can we create a Foreign Key with out Primary Key?
Yes. If the table has Unique Key then it is posible to create a Foreign key constraint.

9) What is the table name,that contains the Primary Key, Unique Key and Foreign Key Information?
INFORMATION_SCHEMA.TABLE_CONSTRAINTS, where CONSTRAINT_TYPE column stores the information of Constraint Type.

Please let me know, if you have simple definitions!!!!
Lets try to prepare list of possible interview questions on "Constraints".
I will answer all of these in next section.
1) What is a Primary Key?
2) What is Unique Key?
3) What is the difference between Primary Key and Unique Key?
4) What is Check Constraint?
5) What is RULE?
6) What is the difference between RULE and Check Constraint?
7) How to create a relationship between two tables?
8) Can we create a Foreign Key with out Primary Key?
9) What is the table name,that contains the Primary Key, Unique Key and Foreign Key Information?
10) What is the table name, that contains Check Constraint Definition?
11) What is the table name, that contains RULE Constraint definition?
12) Can we have RULE and Check Constraint on the same column?
13) Can we apply Integrity Constraints on Computed Columns?
14) Can you write a query to find out the Child Table Name and Parent Table Name and the Columns to join?
15) Can you drop a Parent Table with out affecting its child tables?
16) How to disable and Enable the constraints?
17) What is the order of Constraints execution?
-- Questions from Readers of the DotNetVJ
18) what is difference between Primary Key, Unique Key and Alternative Key?

Let me know if you have any more questions on "Constraints"