-- List all customers.

-- List all books - just title.

-- List all authors.

-- List all royalties.
 
-- List theoretical values in descending order.

-- List bring back dates in ascending order.

-- List horror books.

-- List horror or thriller books.

----------------------------------------------------

-- List books whose price is higher than 5000 or whose number of pages is more than 500.

-- List books whose price is between 1000 and 5000

-- List books whose price is not between 1000 and 5000

-- List books where the topic is literature, history or science

-- List books where the topic is NOT literature, history or science

-- List books where the topic is unknown.

-- List books where the topic is known.


------------------------------------------------------
--The LIKE operator is used in a WHERE clause to search for a specified pattern in a column.

--There are two wildcards often used in conjunction with the LIKE operator:
--     The percent sign (%) represents zero, one, or multiple characters
--     The underscore sign (_) represents one, single character

SYNTAX:
SELECT column1, column2, ...
FROM table_name
WHERE columnN LIKE pattern;

EXAMPLES:
 
-- List the books which title begin with 'The'.

-- List the books which title contains at least two 'a'.

-- List the books which title contains exactly two 'a'.

-- List the books which title ends with 'd'.

-- List the books which title begins with any character, BUT the second character is 'a'.


---------------------------------------------------------
--round() 
--The ROUND() function rounds a number to a specified number of decimal places.
--SYNTAX: 	 ROUND(number, decimals, operation)

-- trunc()


-- length()



--DUAL Table:
--The DUAL is special one row, one column table present by default in all Oracle databases. The owner of DUAL is SYS (SYS owns --the data dictionary, therefore DUAL is part of the data dictionary.) but DUAL can be accessed by every user. The table has a --single VARCHAR2(1) column called DUMMY that has a value of 'X'.
--There may be a situation where we want to query something that is not from a table. For example, getting the current date or --querying a simple arithmetic expression like 2+2.

Examples: 
select 2*3 
from dual;

select sysdate 
from dual;
-- sysdate  - current system date and time


-- EXTRACT