Update README.md

Author: fullstackdeveloper007

README.md

@@ -1,6 +1,66 @@
 # Brush up your knowledge on SQL 
-
-<b>What is the command used to fetch first 5 characters of the string?</b><br/>
+ 
+<b>1. What is the command used to fetch first 5 characters of the string?</b><br/>
 There are many ways to fetch first 5 characters of the string - <br/>
 a) Select SUBSTRING(StudentName,1,5) as studentname from student <br/>
 b) Select RIGHT(Studentname,5) as studentname from student
+<br/>
+<br/> <b>2. How to create a Foreign key </b>
+
+
+a). CREATE TABLE Orders (<br/>
+     OrderID int NOT NULL PRIMARY KEY,<br/>
+    OrderNumber int NOT NULL,<br/>
+    PersonID int FOREIGN KEY REFERENCES Persons(PersonID) <br/>
+);<br/>
+
+b). ALTER TABLE Orders
+ADD FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);
+
+c) ALTER TABLE Orders
+ADD CONSTRAINT FK_PersonOrder
+FOREIGN KEY (PersonID) REFERENCES Persons(PersonID);
+			
+<br/>
+
+<b>3. Handle Exception in SQL</b><br/>
+<p>BEGIN TRY <br/>
+DECLARE @Mynum INT <br/>
+---- Divide by zero Error<br/>
+  SET @Mynum = 10/0<br/>
+  PRINT 'This will not execute'<br/>
+END TRY<br/>
+BEGIN CATCH<br/>
+SELECT @@Error, @@ROWCOUNT<br/>
+SELECT ERROR_NUMBER() AS ErrorNumber, ERROR_SEVERITY() AS ErrorSeverity, ERROR_STATE() AS ErrorState, ERROR_PROCEDURE() AS ErrorProcedure, ERROR_LINE() AS ErrorLine, ERROR_MESSAGE() AS ErrorMessage;<br/>
+END CATCH;<br/>
+GO <p/><br/>
+
+
+<b>4.  RaiseError()</b><br/>
+The RAISERROR statement allows you to generate your own error messages and return these messages back to the application using the same format as a system error or warning message generated by SQL Server Database Engine.<br/><b>Syntax : </b>RAISERROR ( { message_id | message_text | @local_variable }  
+    { ,severity ,state }  
+    [ ,argument [ ,...n ] ] )  
+    [ WITH option [ ,...n ] ];
+
+	 <br/>
+
+<b>5. SQL Transactions</b> <br/>
+<pre class="notranslate">
+	<code> 
+BEGIN TRANSACTION T1	
+	INSERT INTO Customer VALUES (10, 'Code_10', 'Ramesh')
+	INSERT INTO Customer VALUES (11, 'Code_11', 'Suresh') 
+BEGIN TRANSACTION T2
+	INSERT INTO Customer VALUES (12, 'Code_12', 'Priyanka')
+  	INSERT INTO Customer VALUES (13, 'Code_13', 'Preety') 
+  	PRINT @@TRANCOUNT --** Here TRANCOUNT value 2**
+COMMIT TRANSACTION T2 -- This does not physically commit
+  	PRINT @@TRANCOUNT -- **Here TRANCOUNT value 1**
+COMMIT TRANSACTION T1 -- This does a physically commit
+  	PRINT @@TRANCOUNT --** Here TRANCOUNT value 0		**
+</code></pre>
+
+
+ 
+