sql introduction

examples
$query = 'SELECT `first` , `last` FROM `a_database` ORDER BY `id` ';	ist select the two columns with  headeer names, to display in ascending order
$query = 'SELECT `first` , `last` FROM `a_database` WHERE `id`<5  ORDER BY `id` ';	select two columns with header names , to display it hase to pass condtion, which has id is less than 5, that’s display, in an ascending order its display ascending order of id
$query = "SELECT `name` FROM `foods` WHERE `type` = '$fv' ";	type is column header name, select name column header and to display  it matched with fv, which one has matched that rows onl display , from customer
$query = "SELECT `hits` FROM `hits_count` WHERE `id` = 1 ";	select hits column to display it hase to pass condtion, its display only 1 id row
$query = "SELECT `ip` FROM `hits_ipaddress`";	display ip column
$query = "SELECT `ip` FROM `hits_ipaddress`";	display ip column from database
$query = "SELECT `ip` FROM `hits_ipaddress`";
$query = "SELECT `hits` FROM `hits_count` WHERE `id` = 1 ";	select hits column header to display it passs condtion means It display only one row
$query = "SELECT `name` FROM `foods` WHERE `name` LIKE '%$s_text%' ";
$query = "SELECT `id` FROM `users` WHERE `username` = '$username' AND `password` = '$pass_hash' ";
$query = "SELECT `$field` FROM `users` WHERE `id` = '$id' ";
$query =" SELECT `username` FROM `users` WHERE `username` = '$username'";
SELECT `id` FROM `users` WHERE `username` = '' or ''='' AND `password` = '' or ''=''
$query = "SELECT `email` FROM `users` WHERE `id` =$id";
$query = "SELECT `email` FROM `users` WHERE `id` =$id";
SQL can execute queries against a database
SQL can retrieve data from a database
SQL can insert records in a database
SQL can update records in a database
SQL can delete records from a database
SQL can create new databases
SQL can create new tables in a database
SQL can create stored procedures in a database
SQL can create views in a database
SQL can set permissions on tables, procedures, and views
SELECT - extracts data from a database	SELECT * FROM Customers;
UPDATE - updates data in a database	update database1.studentinfo SET firstname ='raju', age =35 where name =1;
DELETE - deletes data from a database	delete from dummy.studentinfo where name=4;
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	drop table dummy.studentinfo;
CREATE INDEX - creates an index (search key)
DROP INDEX - deletes an index
sytax select
SELECT column1, column2, ...
FROM table_name;

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The most common SQL hosting databases are MS SQL Server, Oracle, MySQL, and MS Access.