SQL VS PL/SQL

• SQL Statements can be passed only one at at a time to Oracle for Execution.Each Such         Execution of the SQL statement adds to the network traffic there by decreasing the speed of data     processing especially in a multiuser environment.
• PL/SQL sends an entire block of SQL statements to Oracle,all in one go, thus minimizes the communication between the program block and Oracle considerably,reducing network traffic.
• Since Oracle receives all the SQL statements as single block this code specification is processed much faster than if it received the code specification as one command at a time.
• SQL does not allow defining error messages that popup,if an error is encountered during data manipulation.
• While processing an SQL statement, If an Error occurs oracle displays its own error messages.
• PL/SQL Permits dealing with Errors as required and facilitates displaying user friendly messages when errors are encountered.
• SQL does not have any procedure capabilities such as 

                                                             1.Condition Checking 
                                                             2.Looping
                                                             3.Branching

• These are required so that the data can be tested before its permanent storage whereas PL/SQL development tool not supports SQL data manipulation,but also provides procedural capabilities such as conditional checking,branching & looping. 
• PL/SQL is a high performance transaction processing language since PL/SQL operates over the SQL command, it is a superset of SQL.
• PL/SQL supports Object Oriented Programming.