What are the different type of SQL's statements ?
SQL statements are broadly classified into three. They are 1. DDL – Data Definition Language DDL is used to define the structure that holds the data. For example, Create, Alter, Drop and Truncate table. 2. DML– Data Manipulation Language DML is used for manipulation of the data itself. Typical operations are Insert, Delete, Update and retrieving the data from the table. The Select statement is considered as a limited version of the DML, since it can't change the data in the database. But it can perform operations on data retrieved from the DBMS, before the results are returned to the calling function. 3. DCL– Data Control Language DCL is used to control the visibility of data like granting database access and set privileges to create tables, etc. Example - Grant, Revoke access permission to the user to access data in the database.
Hydrocarbons that contain one or more benzene rings are classified as -
Find the dimensions of the rectangle that has a length 3 meters more that its width and a perimeter equal in value to its area?
Let X be the length and Y be the width of the rectangle. X = Y + 3 Perimeter of the rectangle = 2X + 2Y = 2(Y + 3) + 2Y = 4Y + 6 Area of the rectangle = XY = (Y + 3) Y = YY + 3Y Area and perimeter are equal in value; hence YY + 3Y = 4Y + 6 By solving the above quadratic equation using middle-term splitting method, we get Y = 3 and X = 6