DATA VIEW

DataView Object provides a window into a DataTable that can
be sorted and filtered using the Sort,RowFilter, and
RowStateFilter properties.It also contains the AllowDelete,
AllowEdit,AllowEdit, and AllowNew properties to constrain
user input as needed.

DataTable can have many DataView objects  assigned to it,
allowing the data tobe viewed in many diffirent ways
without requiring the data to be reread from the database.

Example:::

DataTable customer = GetDataTable() //ur datable method
// add new datarow by adding the values
customer.Rows.Add("73OOFUFU","Mohamed","Ilyas",2533.00m);
customer.Rows.Add("3636366H","Idriis","Yassin",25545.00m);
//Sort and display
DataView view = new DataView(customer);
view.sort = "LastName ASC, FirstName ASC, Salary DESC";
GridView gv = new GridView();
gv.EnableViewState = false;
form1.Controls.Add(gv);
// assing ur gridview to dataview
gv.DataSource = veiw;
gv.DataBind();






# 1

data tables holds all the rows of the table where as date
view hold te filtered or reqired rows that are been retrived
on a particular condition

DATA TABLE

<%@ Page Language="C#" Debug="true" %>

<%@ Import Namespace="System.Data.SqlClient" %>

<%@ Import Namespace="System.Data" %>

<script language="C#" runat="server">

private SqlConnectionconn = null;

private SqlCommandcmd = null;

private SqlDataAdapterda = null;

private DataTabledt = null;

private DataRowCollectiondr = null;

private String connString;

private String strSQL;

private void Page_Load(object sender, System.EventArgs e) {

if (!IsPostBack) {
connString = "data source=localhost;uid=test;pwd=test;initial catalog=Northwind";
strSQL = "SELECT LastName, FirstName, Title, HireDate FROM dbo.Employees";

try {
conn = new SqlConnection(connString);
cmd = new SqlCommand(strSQL, conn);
da = new SqlDataAdapter();
da.SelectCommand = cmd;
dt = new DataTable();
conn.Open();
da.Fill(dt);
dr = dt.Rows;

for (inti=0; i<=(dr.Count-1); i++) {
Response.Write(dr[i]["FirstName"].ToString()

+ " " + dr[i]["LastName"].ToString() + " - " +

dr[i]["Title"].ToString() + "<br>");

}
conn.Close();

} catch (SqlException ex) {
Response.Write("Error accessing database: " + ex.ToString());

} catch (Exception ex) {
Response.Write("Exception: " + ex.ToString());

} finally {

if (conn.State == ConnectionState.Open) {
conn.Close();

}
conn.Dispose();

} } }

</script>





<%@ Page Language="C#" Debug="true" %>

<%@ Import Namespace="System.Data.SqlClient" %>

<%@ Import Namespace="System.Data" %>

<script language="C#" runat="server">

private SqlConnectionconn = null;

private SqlCommandcmd = null;

private SqlDataAdapterda = null;

private DataTabledt = null;

private DataRow[] dr = null;

private String connString;

private String strSQL;

private void Page_Load(object sender, System.EventArgs e) {

if (!IsPostBack) {
connString = "data source=localhost;uid=test;pwd=test;initial catalog=Northwind";
strSQL = "SELECT LastName, FirstName, Title, HireDate FROM dbo.Employees";

try {
conn = new SqlConnection(connString);
cmd = new SqlCommand(strSQL, conn);
da = new SqlDataAdapter();
da.SelectCommand = cmd;
dt = new DataTable();
conn.Open();
da.Fill(dt);
dgTest.DataSource = dt;
dgTest.DataBind();
conn.Close();

} finally {

if (conn.State == ConnectionState.Open) {
conn.Close();

}
conn.Dispose();

} } }

</script>

<asp:DataGrid id="dgTest" runat="Server"></asp:DataGrid>

What is SQL Profiler?

SQL Profiler is a graphical tool that allows system administrators to monitor events in an instance of Microsoft SQL Server. You can capture and save data about each event to a file or SQL Server table to analyze later. For example, you can monitor a production environment to see which stored procedures are hampering performances by executing too slowly.
Use SQL Profiler to monitor only the events in which you are interested. If traces are becoming too large, you can filter them based on the information you want, so that only a subset of the event data is collected. Monitoring too many events adds overhead to the server and the monitoring process and can cause the trace file or trace table to grow very large, especially when the monitoring process takes place over a long period of time.

What are the properties and different Types of Sub-Queries?

1. Properties of Sub-Query
   1. A sub-query must be enclosed in the parenthesis.
   2. A sub-query must be put in the right hand of the comparison operator, and
   3. A sub-query cannot contain an ORDER-BY clause.
   4. A query can contain more than one sub-query.
2. Types of Sub-Query
   1. Single-row sub-query, where the sub-query returns only one row.
   2. Multiple-row sub-query, where the sub-query returns multiple rows,. and
   3. Multiple column sub-query, where the sub-query returns multiple columns

What is difference between DELETE and TRUNCATE commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

1. TRUNCATE:
   1. TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
   2. TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log.
   3. TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column.
   4. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
   5. TRUNCATE cannot be rolled back.
   6. TRUNCATE is DDL Command.
   7. TRUNCATE Resets identity of the table
2. DELETE:
   1. DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.
   2. If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.
   3. DELETE Can be used with or without a WHERE clause
   4. DELETE Activates Triggers.
   5. DELETE can be rolled back.
   6. DELETE is DML Command.
   7. DELETE does not reset identity of the table.

Note: DELETE and TRUNCATE both can be rolled back when surrounded by TRANSACTION if the current session is not closed. If TRUNCATE is written in Query Editor surrounded by TRANSACTION and if session is closed, it can not be rolled back but DELETE can be rolled back.

What are different types of Collation Sensitivity?

1. Case sensitivity - A and a, B and b, etc.
2. Accent sensitivity
3. Kana Sensitivity - When Japanese kana characters Hiragana and Katakana are treated differently, it is called Kana sensitive.
4. Width sensitivity - A single-byte character (half-width) and the same character represented as a double-byte character (full-width) are treated differently than it is width sensitive.

What are the different index configurations a table can have?

A table can have one of the following index configurations:

1. No indexes
2. A clustered index
3. A clustered index and many nonclustered indexes
4. A nonclustered index
5. Many nonclustered indexes

What is User Defined Functions? What kind of User-Defined Functions can be created?

User-Defined Functions allow defining its own T-SQL functions that can accept 0 or more parameters and return a single scalar data value or a table data type.
Different Kinds of User-Defined Functions created are:

1. Scalar User-Defined Function A Scalar user-defined function returns one of the scalar data types. Text, ntext, image and timestamp data types are not supported. These are the type of user-defined functions that most developers are used to in other programming languages. You pass in 0 to many parameters and you get a return value.
2. Inline Table-Value User-Defined Function An Inline Table-Value user-defined function returns a table data type and is an exceptional alternative to a view as the user-defined function can pass parameters into a T-SQL select command and in essence provide us with a parameterized, non-updateable view of the underlying tables.
3. Multi-statement Table-Value User-Defined Function A Multi-Statement Table-Value user-defined function returns a table and is also an exceptional alternative to a view as the function can support multiple T-SQL statements to build the final result where the view is limited to a single SELECT statement. Also, the ability to pass parameters into a TSQL select command or a group of them gives us the capability to in essence create a parameterized, non-updateable view of the data in the underlying tables. Within the create function command you must define the table structure that is being returned. After creating this type of user-defined function, It can be used in the FROM clause of a T-SQL command unlike the behavior found when using a stored procedure which can also return record sets.

What are the advantages of using Stored Procedures?

1. Stored procedure can reduced network traffic and latency, boosting application performance.
2. Stored procedure execution plans can be reused, staying cached in SQL Server's memory, reducing server overhead.
3. Stored procedures help promote code reuse.
4. Stored procedures can encapsulate logic. You can change stored procedure code without affecting clients.
5. Stored procedures provide better security to your data.

What is PRIMARY KEY?What is UNIQUE KEY constraint?What is FOREIGN KEY?

A PRIMARY KEY constraint is a unique identifier for a row within a database table. Every table should have a primary key constraint to uniquely identify each row and only one primary key constraint can be created for each table. The primary key constraints are used to enforce entity integrity.

 What is UNIQUE KEY constraint?

A UNIQUE constraint enforces the uniqueness of the values in a set of columns, so no duplicate values are entered. The unique key constraints are used to enforce entity integrity as the primary key constraints.

 What is FOREIGN KEY?

A FOREIGN KEY constraint prevents any actions that would destroy links between tables with the corresponding data values. A foreign key in one table points to a primary key in another table. Foreign keys prevent actions that would leave rows with foreign key values when there are no primary keys with that value. The foreign key constraints are used to enforce referential integrity.

What is the STUFF function and how does it differ from the REPLACE function?

STUFF function is used to overwrite existing characters. Using this syntax, STUFF (string_expression, start, length, replacement_characters), string_expression is the string that will have characters substituted, start is the starting position, length is the number of characters in the string that are substituted, and replacement_characters are the new characters interjected into the string. REPLACE function to replace existing characters of all occurrences. Using the syntax REPLACE (string_expression, search_string, replacement_string), where every incidence of search_string found in the string_expression will be replaced with replacement_string.

What is the difference between a Local and a Global temporary table?

1. A local temporary table exists only for the duration of a connection or, if defined inside a compound statement, for the duration of the compound statement.
2. A global temporary table remains in the database permanently, but the rows exist only within a given connection. When connection is closed, the data in the global temporary table disappears. However, the table definition remains with the database for access when database is opened next time.

What does it mean to have QUOTED_IDENTIFIER ON? What are the implications of having it OFF?

When SET QUOTED_IDENTIFIER is ON, identifiers can be delimited by double quotation marks, and literals must be delimited by single quotation marks. When SET QUOTED_IDENTIFIER is OFF, identifiers cannot be quoted and must follow all Transact-SQL rules for identifiers.

Name 3 ways to get an accurate count of the number of records in a table?

SELECT * FROM table1
SELECT COUNT(*) FROM table1
SELECT rows FROM sysindexes WHERE id = OBJECT_ID(table1) AND indid < 2

What is Log Shipping?

Log shipping is the process of automating the backup of database and transaction log files on a production SQL server, and then restoring them onto a standby server. Enterprise Editions only supports log shipping. In log shipping the transactional log file from one server is automatically updated into the backup database on the other server. If one server fails, the other server will have the same db and can be used this as the Disaster Recovery plan. The key feature of log shipping is that it will automatically backup transaction logs throughout the day and automatically restore them on the standby server at defined interval.

Which command using Query Analyzer will give you the version of SQL server and operating system?

SELECT SERVERPROPERTY ('productversion'), SERVERPROPERTY ('productlevel'), SERVERPROPERTY ('edition').

What is SQL Profiler?

SQL Profiler is a graphical tool that allows system administrators to monitor events in an instance of Microsoft SQL Server. You can capture and save data about each event to a file or SQL Server table to analyze later. For example, you can monitor a production environment to see which stored procedures are hampering performances by executing too slowly.
Use SQL Profiler to monitor only the events in which you are interested. If traces are becoming too large, you can filter them based on the information you want, so that only a subset of the event data is collected. Monitoring too many events adds overhead to the server and the monitoring process and can cause the trace file or trace table to grow very large, especially when the monitoring process takes place over a long period of time.

What are the properties and different Types of Sub-Queries?

1. Properties of Sub-Query
   1. A sub-query must be enclosed in the parenthesis.
   2. A sub-query must be put in the right hand of the comparison operator, and
   3. A sub-query cannot contain an ORDER-BY clause.
   4. A query can contain more than one sub-query.
2. Types of Sub-Query
   1. Single-row sub-query, where the sub-query returns only one row.
   2. Multiple-row sub-query, where the sub-query returns multiple rows,. and
   3. Multiple column sub-query, where the sub-query returns multiple columns

What is difference between DELETE and TRUNCATE commands?

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

1. TRUNCATE:
   1. TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
   2. TRUNCATE removes the data by deallocating the data pages used to store the table's data, and only the page deallocations are recorded in the transaction log.
   3. TRUNCATE removes all rows from a table, but the table structure, its columns, constraints, indexes and so on, remains. The counter used by an identity for new rows is reset to the seed for the column.
   4. You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
   5. TRUNCATE cannot be rolled back.
   6. TRUNCATE is DDL Command.
   7. TRUNCATE Resets identity of the table
2. DELETE:
   1. DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.
   2. If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.
   3. DELETE Can be used with or without a WHERE clause
   4. DELETE Activates Triggers.
   5. DELETE can be rolled back.
   6. DELETE is DML Command.
   7. DELETE does not reset identity of the table.

What's the difference between a primary key and a unique key?

Both primary key and unique key enforces uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.