How does php insert 1000 pieces of data into mysql?

Php inserts 1000 data records into mysql. how can this problem be solved ??? For ($ i1; $ I & lt; 1000; $ I ++) {& nbsp; $ id. php inserts 1000 pieces of data into mysql. how to write ???
For ($ I = 1; $ I <= 1000; $ I ++)
{
USD id = "100 ";
$ Username = "xm ";

$ SQL = "insert into tb_user (id, username) values ('$ ID',' $ username ')";
Mysql_query ($ SQL );
}


I didn't set id and username as the primary key,

But insert a piece of data. what is the problem? Thank you!

------ Solution --------------------
Do not operate databases frequently. Suggestions

PHP code

For ($ I = 1; $ I <= 1000; $ I ++) {$ id = '000000'; $ username = 'xm '; $ SQL [] = '('. $ id. ',"'. $ username. '")';} mysql_query ('Insert into tb_user (id, username) values '. implode (',', $ SQL ));