What are the difference between DDL, DML and DCL commands?

DDL

Data Definition Language (DDL) statements are used to define the database structure or schema. Some examples:
CREATE - to create objects in the database
ALTER - alters the structure of the database
DROP - delete objects from the database
TRUNCATE - remove all records from a table, including all spaces allocated for the records are removed
COMMENT - add comments to the data dictionary
RENAME - rename an object

RAID Concept & Levels

RAID (originally redundant array of inexpensive disks; now commonly redundant array of independent disks) is a data storage virtualization technology that combines multiple disk drive components into a logical unit for the purposes of data redundancy or performance improvement.

Displays a list of files and sub directories in a directory in CMD Prompt.

 DIR [ drive:][path][file-name] [/A[[:]attributes]] [/B] [/C] [/D] [/L] [/N]
  [/O[[:]sortorder]] [/P] [/Q] [/R] [/S] [/T[[:]timefield]] [/W] [/X] [/4]

  [drive:][path][filename]
          Specifies drive, directory, and/or files to list.

  /A          Displays files with specified attributes.
           D  Directories                R  Read-only files
           H  Hidden files               A  Files ready for archiving
           S  System files               I  Not content indexed files
           L  Re parse Points        -  Prefix meaning not

Just set type of desired file attribute, in your case /A:D (directory)

dir /s/b/o:n/A:D > filename.txt

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CASCADE in SQL Server (Foreign & Primary Key Constraints)

We have several tables in an SQL database referencing each other with foreign key constraints. If we need to delete a row in one of these tables as well as all other rows that reference it, then we have two options. The first option is to execute an explicit DELETE statement for each table that contains referencing rows and then finish by deleting the referenced row (this order is important if we don’t want to violate any foreign key constraints). The other option is to declare our foreign keys as ON DELETE CASCADE. This clause tells the database to automatically delete the referencing row if the row it references is deleted.

Select * from dbo.ProductDetails
Select * from dbo.Products

Suspect Query for MS SQL 2005

How To Repair A Suspect Database In MSSQL 2005:

Issue
You have a database in MSSQL that is tagged as (suspect) and you are unable to connect to the database.

Possible Causes
The database could have become corrupted.
There is not enough space available for the SQL Server to recover the database during startup.
The database cannot be opened due to inaccessible files or insufficient memory or disk space.
The database files are being held by operating system, third party backup software etc.
There was an unexpected SQL Server Shutdown, power failure or a hardware failure.

Get Client IP Address in SQL Server..

Execute the below function and call this function through a Stored Procedure. It will return the IP address of the client system.

CREATE FUNCTION [dbo].[GetCurrentIP] ()
RETURNS varchar(255)
AS
BEGIN
    DECLARE @IP_Address varchar(255);

    SELECT @IP_Address = client_net_address
    FROM sys.dm_exec_connections
    WHERE Session_id = @@SPID;

    Return @IP_Address;
END


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What is NAS, SAN, DAS ?

NAS stands for Network Attached Storage. It differs from traditional, directly attached storage in that, in NAS, the operating system and other software on the NAS product are dedicated solely to data storage.

SAN stands for Storage Area Network. A SAN is a network designed to attach storage hardware and software to servers. SANs generally come in two forms: as a network primarily dedicated to transferring data between computer systems and storage systems, or as a complete system that includes all of the storage elements and computer systems within the same network.

DAS stands for Directly Attached Storage. DAS is generally used to differentiate between storage systems directly attached to a server or workstation and NAS and SAN setups.


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