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The SQL CASE statement has WHEN, THEN, and ELSE clauses along with an END terminator. Example DECLARE @Gender VARCHAR ( 50 ) SET @Gender = 'Male' SELECT CASE @Gender           WHEN 'Male'    THEN 'M'           WHEN 'Female' THEN 'F'           ELSE   null END        as 'Gender' SQL Server compares this @Gender   to the expression   and when the values match, it returns the THEN clauses ‘ M’ or ‘ F ’. If none of the WHEN clauses match then it will return ‘ null ’ value

Use NEWID() function to create unique guid. SELECT NEWID() Example If you want to generate a new Guid (uniqueidentifier) in SQL server the you can simply use the NEWID() function. CREATE TABLE Employees (       EID   UNIQUEIDENTIFIER ,       ENAME VARCHAR ( 100 ) ) INSERT INTO Employees VALUES ( NEWID (), 'ABC' ) INSERT INTO Employees VALUES ( NEWID (), 'PQR' ) SELECT * FROM Employees

Constraints are allows us to enforce rules in our database. SQL Server supports 6 types of constraints. A Constraint is a property that we can assign to column in table. By assigning constraint property on column we can prevent the users to enter inconsistent of data in columns. We can assign these Constraint properties during the time of creation of table (By Using CREATE TABLE statement) or during the time of changing the existing table structure (By Using ALTER TABLE statement)      Primary Key Constraint       Unique Key Constraint       Foreign Key Constraint       Not Null Constraint       C heck Constraint      Default Constraint

The DEFAULT constraint is used to insert a default value into a column. The default value will be added to all new records, if no other value is specified. Example The following SQL query creates a DEFAULT constraint on the " AddedDate " column when the " Emp " table is created CREATE TABLE Emp (             EID INT PRIMARY KEY IDENTITY ,             ENAME VARCHAR ( 100 ),             EAGE INT ,             AddedDate DateTime Default GetDate () ) Insert Record into the Emp table , here we are not specified any value into the “ AddedDate ” INSERT INTO Emp ( ENAME , EAGE ) VALUES ( 'abc' , 24 ) AddedDate will be insert the default value (means the Current Date) into the table  Now with Column value is specified INSERT INTO Emp ( ENAME , EAGE , AddedDate ) VALUES ( 'abc' , 24 , getdate ())

Primary key constraint is used to uniquely identify each record in database table.   It won’t allow repetition or duplication of data Every table should have a primary key constraint to uniquely identify each row. Each table is having only one primary key constraint and it contains only unique values. Primary key constraint doesn’t accept null values Example Here is the syntax to define EID attribute as a primary key in a Employee table. CREATE TABLE Employee (             EID INT PRIMARY KEY IDENTITY NOT NULL,             ENAME VARCHAR ( 50 ),             SALARY DECIMAL ( 10 , 2 ),             DEPT VARCHAR ( 50 ) )

NULL is   unknown   or   missing data in table. When you create a new NOT NULL constraint on a   column , SQL Server checks the column’s current contents for any NULL values. If the column currently contains NULL values, the constraint creation fails. Otherwise, SQL Server adds the NOT NULL constraint and any future   INSERT   or   UPDATE   commands that would cause the existence of a NULL value fail. Example CREATE TABLE Employee (           EID INT PRIMARY KEY IDENTITY NOT NULL,           ENAME VARCHAR ( 50 ) NOT NULL,           SALARY DECIMAL ( 10 , 2 ) NOT NULL,           DEPT VARCHAR ( 50 ) ) INSERT INTO Employee ( ENAME , SALARY , DEPT ) VALUES ( 'abc' , 20000 , 'HR' ) The following SQL enforces the " EID " column and the " ENAME, SALARY " column to not accept NULL values:    INSERT INTO Employee ( ENAME , DEPT ) VALUES ( 'pqr' , 'HR' ) Msg 515

Automatic web page refresh can be implemented in an ASP.NET (.aspx) web-page by adding some HTML code in the header section. < meta http-equiv ="refresh" content ="15"> Set the time according to your requirement in content="time in sec". For adding Aspx server side the Page_Load function to set it, as shown below:  Response.AppendHeader("Refresh", "15")

Connected Disconnected It is connection oriented. It is dis_connection oriented. Datareader DataSet Connected methods gives faster performance Disconnected get low in speed and performance. connected can hold the data of single table disconnected can hold multiple tables of data connected you need to use a read only forward only data reader disconnected you cannot Data Reader can't persist the data Data Set can persist the data It is Read only, we can't update the data. We can update data