Structured Query Language (1 Mark Questions)

1. None of the aboveWhich is the subset of SQL command used to manipulate Oracle Database Structures:
• DDL(Data Definition Language)
• DML (Data Manipulation Language)
• Both
• None of the above
2. What is the difference between count(*) and count(<col>).
3. "Pay" is a column name for the Pay of staff  in a table "Schools".

   The following SQL queries are used to find 
   the total number of paid employees:  
   
   i) SELECT count(*) FROM Schools;
   ii) SELECT count(Pay) FROM Schools;
   

   The outputs obtained are 40 and 39 in both the queries respectively.
   What is the reason behind different output?
4. What is the use of COMMIT in sql ?
5. What is the function of ALTER command?
6. NULL value means :
• 0 value
• 1 value
• None value
• None of the above
7.