SQL Basics

SELECT - extracts data from a database
UPDATE - updates data in a database
DELETE - deletes data from a database
INSERT INTO - inserts new data into a database
CREATE DATABASE - creates a new database
ALTER DATABASE - modifies a database
CREATE TABLE - creates a new table
ALTER TABLE - modifies a table
DROP TABLE - deletes a table
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index
DISTINCT - for all the distinct values only
WHERE - to raise a condition
ORDER BY - to sort in asc/desc order.
LIMIT - to limit the number of records to display.
COUNT(col_name) / AVG(col_name) / SUM(col_name) - to count total rows matching the condition / avg/sum of rows if they are numeric.
LIKE - type of condition where the values similar/alike as given condition.
BETWEEN - selects in give range inclusive of given values.

SELECT * FROM table_name;																results all the values.
SELECT DISTINCT FROM table_name;  														results all the distinct values only.
SELECT DISTINCT coloumn_name FROM table_name; 											results all the distinct values in coloumn only.
SELECT * FROM table_name WHERE condition; results values satisfying that condition.		AND/OR/NOT operators are also used.
SELECT * FROM table_name ORDER BY coloumn DESC;											desc order by country. without mentioning desc, it is Asc.
SELECT * FROM table_name ORDER BY coloumn1 ASC, coloumn2 DESC;							Asc of coloumn1, then desc of coloumn2 within.
INSERT INTO table_name (col1,col2,col3) VALUES (val1,val2,val3);						why can't we add in rows.
UPDATE table_name SET col1=val1, col2=val2, col3=val3 WHERE condition					updates values using set command with where condition.
DELETE FROM table_name WHERE col2=val;													Deletes that row.
SELECT coloumns/* FROM table_name WHERE condition LIMIT number;							sets the limit for output count.
SELECT * FROM table_name WHERE condition LIKE 'a%'/'_a%';								displays elements starts with 'a'/ second letter is 'a'.
SELECT * FROM Customers WHERE Country IN (SELECT Country FROM Suppliers);				selects all customers that are same countries as the suppliers.




MY EXAMPLE:-
CREATE TABLE fav_items (id INT, name VARCHAR(20), quantity INT, rating REAL);
INSERT INTO fav_items(id,name,quantity,rating) 
VALUES ('1','veggies','1','4'),
('2','Coco Water','12','4.2'),
('3','Cake Rusk','15','4.4'),
('4','BlueBunny-BananaSplit','1','4.4'),
('5','DairyMilk','1','4.6'),
('6','Cake Rusk','15','4.4');
SELECT * FROM fav_items WHERE rating > '4' OR '3.99' ORDER BY rating DESC;
UPDATE fav_items
SET name = 'Hash Browns', quantity = 10, rating = 3.9 WHERE id = 6 ;