Explain logical database components.

Answer
The logical components are usually used to connect to the database. Any object that a user can use to access or connect to the database is a logical component. Triggers, tables, procedures, views, keys etc are typical examples.

What are the database objects? Explain them in brief.

Answer
Database objects such as tables, primary key, and foreign key describe the structure of the content of a database. These objects also represent the properties of a server. Server side objects are objects that reside on the server but not in the database. Typical examples of server side objects include, logins, user defined error messages etc. The database objects are contained in the database project while the server objects are contained in the server project. These objects are defined in a .sql file. Most of these objects are defined in a separate file depending on the scenario. E.g it is necessary to specify columns in the same file where the table is defined.

Illustrate physical database architecture in brief.

Answer
The physical database architecture describes how the database and files are organized in a SQL server.

Pages and extents: these describe how the data is stored

Physical Database Files and File groups :- describes the operating system files used to store data and logs.

Space Allocation and Reuse :- Describes the algorithms used for space allocation.

Table and Index Architecture :- Describes the way pages for tables can be indexed

What are pages and Extents?

Answer
A page is a unit of data storage in SQL. The size of a page is 8Kb. A page has a header and a body. Different types of pages are: Date, text, index , page free space etc. The data rows are put on the page serially after the header.

Extents are units in which space is allocated to tables and indexes. An extent is 8 continuous pages. SQL Server has two types of extents: uniform and mixed extent. For efficient allocation, the SQL server does not allocate whole extents to tables with small amounts of data

SQL Server constraints

What are constraints in SQL Server?

Constraints enforce the data integrity to the database and protect columns of the table from unwanted values. NOT NULL, CHECK, UNIQUE, PRIMARY KEY, FOREIGN KEY are the types of contraints define in SQL Server.

Define default constraint?

Default constraint is used to fill column with default value defined during creation of table if nothing is supplied while inserting data. IDENTITY columns and timestamp columns can't be associated with default constraint.