Untitled

Order by clause:
order by is used to sot the data in the assending or descending order.

syntax:- selct * from tablename order by column_name asc/desc

select * from Orders order by item asc;

when we short data in any filter condition we use where and order by clause;
sequence is mandatory:
1 where
2.order by
example:
select * from Orders where customer_id=4  order by item desc ;

----------------------------------------------------------------------------------------
Update staement:
update staement is use for modify the existing records.

 ex:-update Orders set item="keypad" where order_id=4;

modify multiple colums:
 ex:update Orders set item="keyboard" ,customer_id=5 where order_id=4;

 exmple : modify columns in multiple values
update Orders set customer_id=5 where order_id in (2,3) ;
update Orders set customer_id=3 where order_id =2 or item="Keyboard";
update Orders set customer_id=3 where order_id =2 and item="Keyboard";

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

difference between update and alter:

alter:1. data defination lang(DDL)
      2.alter command will perform structure level.
      3.syntax alter table tablename (modify/add/rename) Drop column column_name


update:1. data manipulation lang(DML)
       2.update command will perform on data level.
       3 syntax :-update table_name set column_name=values



---------------------------------------------------------------------------------------------
group by :
it is used for grouping data in given column.
group by is used with agreegate function (sum(), count(), avg(),min(),max().
syntax:
select column_name() from table_name group by column_name;
ex:-select count(*) as count,country from Customers  group by country;

select count(*) as count,country from Customers  group by country order by country desc;

sequence:- where
           group by
           order by

group by with where statement
select count(*) as count,country from Customers where customer_id in (2,4)  group by country order by country desc;