UNION SQL syntax is used to select information from two tables. But it selects only distinct records from both the table, while UNION ALL selects all records from both the tables.
Note :- Selected records should have same datatype or else the syntax will not work.


You can use Having Clause with the GROUP BY function in a query and WHERE Clause is applied to each row before they are part of the GROUP BY function in a query.

Following are difference between them :-
√ DELETE TABLE syntax logs the deletes thus make the delete operation slow. TRUNCATE table does not log any information but it logs information about de-allocation of data page of the table so TRUNCATE table is faster as
compared to delete table.
√ DELETE table can have criteria while TRUNCATE can not.
√ TRUNCATE table can not trigger.
Note :- Thanks to all the readers for pointing out

Clone: – It only copies structure, does not copy data.
Copy: – Copies both structure and data.

Following are some major differences between dataset and datareader :-
√ DataReader provides forward-only and read-only access to data, while the DataSet object can hold more than one table (in other words more than onerowset) from the same data source as well as the relationships between them.
√ Dataset is a disconnected architecture while datareader is connected architecture.
√ Dataset can persist contents while datareader can not persist contents, they are forward only.

A Datagrid, Datalist and Repeater are all ASP.NET data Web controls.
They have many things in common like DataSource Property, DataBind Method ItemDataBound and ItemCreated.
When you assign the DataSource Property of a Datagrid to a DataSet then each DataRow present in the DataRow Collection of DataTable is assigned to a corresponding DataGridItem and this is same for the rest of the two controls also. But The HTML code generated for a Datagrid has an HTML TABLE <ROW> element created for the particular
DataRow and its a Table form representation with Columns and Rows.
For a Datalist its an Array of Rows and based on the Template Selected and the RepeatColumn Property value We can specify how many DataSource records should appear per HTML <table> row. In short in datagrid we have one record per row, but in datalist we can have five or six rows per row.
For a Repeater Control, the Datarecords to be displayed depends upon the Templates specified and the only HTML generated is the due to the Templates. In addition to these, Datagrid has a in-built support for Sort, Filter and paging the Data,
which is not possible when using a DataList and for a Repeater Control we would require
to write an explicit code to do paging.

Session object store information between HTTP requests for a particular user, while application object are global across users.

“Web.config” files apply settings to each web application, while “Machine.config” file
apply settings to all ASP.NET applications.

System.String is immutable; System.StringBuilder can have mutable string where a variety
of operations can be performed.

A thread is a path of execution that run on CPU.

A process is a collection of threads that share the same virtual memory.

A process has at least one thread of execution, and a thread always run in a process context.